Siman 562

There are four types of fasts. Two are from the words of the Torah, one fixed and the second not fixed. And similarly, two are from the words of the Scribes, one fixed and the second not fixed. How so? The fixed one from the words of the Torah is Yom Kippur once a year. And that which is not fixed—this is a fast that one accepted upon himself by a vow to fast a day or such and such days. And regarding this it is said (Numbers 30:3): "If a man makes a vow... according to all that proceeds from his mouth he shall do." And even if he vowed to fast on Shabbat or a Yom Tov—the vow takes effect, as I wrote in Yoreh Deah siman 215, see there. And the fixed ones from the words of the Scribes are five days in the year: the four fasts and Ta'anit Esther. And that which is not fixed from the words of the Scribes are for any trouble that should not come, as we will explain with the help of Heaven.

This is the wording of the Rambam at the beginning of the laws of fasts: It is a positive commandment from the Torah to cry out and to sound the trumpets over every trouble that comes upon the community, as it is said: "Against the adversary that oppresses you, then you shall sound an alarm with the trumpets." Meaning: anything that distresses you, such as drought, pestilence, locusts, and the like—cry out over them and sound the trumpets. And this matter is among the paths of repentance, for at the time that a trouble comes, and they cry out over it and sound the trumpets—everyone will know that because of their evil deeds it has gone badly for them, as it is written: "Your iniquities have turned away these things...", and this is what will cause the removal of the trouble from upon them. But if they do not cry out and do not sound the trumpets, but rather say: this thing is of the custom of the world that occurred, and it is a happenstance—behold, this is a way of cruelty, and it causes them to cling to their evil deeds, and the trouble will add other troubles. It is that which is written in the Torah: "And if you walk with Me with happenstance, then I will also walk with you in the heat of happenstance." Meaning: when I bring upon you trouble so that you shall repent, if you say that it is happenstance—I will add to you that happenstance. Thus far his words. And he wrote further:

It is by the words of the scribes to fast for any trouble that comes upon the community, until they receive mercy from Heaven. And on these fast days, they cry out in prayers, and plead with supplications, and sound the alarm with trumpets alone. And if they were in the Temple—they sound the alarm with trumpets and a shofar, the shofar shortens and the trumpets lengthen, for the commandment of the day is with trumpets. And they do not sound the trumpets and shofar as one except in the Temple, as it is said: "With trumpets and the sound of the shofar—sound the alarm before the King, Hashem..." Thus far his words, meaning: only before Hashem in the Temple shall you sound the alarm with both things, and not in the borders. However, in any event, we have learned that for a trouble one is obligated to fast by the words of the scribes. And according to the opinion of the Rambam, even an individual upon whom a trouble comes is obligated to fast, and it will be explained in siman 578. And communal troubles will be explained in siman 575 and siman 576 with the help of Heaven.

And we have a question regarding this: for behold, in this siman it will be explained that any fast that one did not accept upon himself while it was still day at the time of mincha – is not called a fast. And it is an explicit Gemara in Taanit (12a). And this is certainly only regarding a fast of a vow, for regarding the fixed fasts – acceptance is not relevant, as even one who is accustomed to fasting the Ten Days of Repentance – does not require acceptance, as our teacher, the Beit Yosef, wrote in section 2, and as will be explained. And all the more so communal fasts on account of troubles, it is obvious that they do not require acceptance. For only an individual fast requires acceptance, as the Tur and the Shulchan Aruch wrote in section 5, that any fast that the individual did not accept upon himself while it was still day – is not a fast, see there. And it is a great wonder: since it is a commandment from the Torah on account of his vow, if so, what does it matter to me if he accepted it while it was still day or did not accept it? Is this any worse than one who vows "I will not eat this loaf," and the like? And while it is true that one could say that he is obligated to fulfill his vow, but he has no reward for a fast if he did not accept it while it was still day. But the difficulty is clear.

However, the truth is that a standard acceptance of a fast is not of the nature of a neder. This is the wording of the Ramban in the laws of nedarim at the end of the ninth chapter: For this neder here is not a literal neder that he expressed with the language of "it is incumbent upon me," but rather it is a mere acceptance of a fast. And the acceptance of a fast is not as severe as literal nedarim to uproot a Yom Tov, even those of Megillat Ta'anit... Thus far his words. And so wrote the Ritva there, and this is his wording: And the reason for the matter is that the acceptance of a fast is neither a neder of prohibition nor a handle of a neder to prohibit food and drink upon himself on that day, but rather it is an affliction that he accepted upon himself to perform the mitzvah of repentance on that day. And it is not implied that this should be... Thus far his words. And also the Nimukei Yosef wrote there similarly, and this is his wording: For here it is literally a neder of a prohibition on the object, where he said "Konam upon me any food...", but there it is not a literal neder, but rather an acceptance of a fast that he accepted upon himself to fast. And it is only like one who accepts upon himself to perform a mitzvah, for there is no prohibition on the object in his acceptance. And it is not as severe as literal nedarim. Therefore they said: "A person may borrow his fast and repay it...". Consequently, the acceptance of a fast is not a neder, and therefore it is only rabbinic because he transgressed his acceptance. And it does not require the release of a sage. Thus far his words. And this is the intention of the Ra'avad in the glosses in the third chapter of Nedarim, law 9, regarding what the Rambam wrote that one who vows to fast on Shabbat or on Yom Tov is obligated to fast, he wrote in this language: Specifically when he said "it is incumbent upon me," but if he said "I am hereby in a state of fasting today" – it is forbidden to fast. Thus far his words (and the Magen Avraham alluded to it in siman 570, subsection 2, see there). And according to this, according to these our teachers, a fast that is from the Torah is only when one says "it is incumbent upon me not to eat" or "Konam upon me not to eat this day," and in such a case he does not require an acceptance of the fast. But when he said "I am hereby in a state of fasting tomorrow" or "for such-and-such a day" – it is only rabbinic. And he must accept it at the time of Mincha, and if not, he does not need to fast. And behold, in Yoreh Deah siman 215 we explained that the Rambam does not hold accordingly, and according to him we will need to say as I wrote at the end of the previous section. And see what I wrote in section 20.

And according to this, another new law emerges for us. For behold, regarding the definition of the obligation to fast, even on Tisha B'Av which is very stringent, we ruled in siman 554 that even a person who is ill but not in danger does not need to fast, because in a case of illness the rabbis did not decree; see there. And according to this, regarding a private fast, which is like a vow which is from the Torah—one would be obligated to fast, and would not be exempt unless there is danger to life. Yet behold, we do not do so, for all those who are accustomed to fast on certain days like a Yahrtzeit, and the Ten Days of Repentance, and the eve of Rosh Chodesh where they were accustomed to fast so, for the custom is like a vow, and we are very lenient regarding them, even more so than the four fasts. Rather, it is certain that an ordinary fast is rabbinic. And if they truly accepted it with the language of "konam" or with the language of "behold it is incumbent upon me," which is a Torah matter, it would be forbidden in a case where there is no danger to life (so it appears in my humble opinion). However, regarding this we have already explained in Yoreh Deah siman 214 that a custom is not in the category of a vow at all. And that which we hold there, that to transgress a custom requires annulment—this is merely a stringency; see there.

And according to this, it appears clear that several laws that exist regarding a taanit—such as that one does not fast for hours according to what will be explained, or that any taanit where the sun did not set upon him is not called a taanit, or that which we hold that a person may borrow his taanit and repay it—this is only in a standard case where he accepted upon himself to fast. But if he said, "Konam upon me from eating and drinking such and such hours," he must fulfill his neder, and no more. And in this, it is impossible to borrow for another time and to repay, for a neder is separate and a taanit is separate. For in a neder, the language of "taanit" is not used, as a neder must forbid the object upon his person, and this is not applicable with the language of taanit. And even if he said, "Behold, I vow to fast," this is not the language of a neder (Magen Avraham siman 570, subsection 2); and likewise if he said, "Behold, it is upon me to fast"; rather, it is when he says, "Behold, I vow from eating and from drinking tomorrow or such and such a day," or "Behold, it is upon me not to eat and not to drink," or "Konam from eating and drinking." But any language of "taanit" is an acceptance of a taanit and not a neder. (And this is what they said in Taanit 12b: Rav Yehuda said in the name of Rav: A person may borrow his taanit and repay it. When I said this before Shmuel, he said to me: Did he accept a neder upon himself? etc., see there. And more will be explained regarding this in siman 568.)

Any fast upon which the sun did not set—that is, one did not complete it until the emergence of the stars, which is to say three medium stars when they are seen, or when the moon shines strongly upon the earth—is not a fast. And if his intention is to eat before this time, he does not pray "Anenu." According to this, it is also forbidden to eat during bein hashemashot. And even though in Pesachim (54b) we say that only regarding Tisha B'Av is its bein hashemashot forbidden like Yom Kippur, and it is explicitly explained that other fasts are permitted during bein hashemashot—this is regarding the beginning of the day at the start of the fast. However, at the conclusion of the day at the end of the fast, in every fast it is forbidden during bein hashemashot, for due to doubt its sanctity has not departed and its sanctity has not entered (Beit Yosef and Magen Avraham).

And it is true that the Mordekhai wrote so in the first chapter of Taanit, and the Rosh there (siman 12). But the Rosh himself at the end of the second chapter of Shabbat wrote in the name of our teacher Yonah that during bein hashemashot it is permitted, see there. And so it appears to me is the opinion of the Rambam, for this law—that any fast where the sun did not set upon it is not called a fast—is not found in his composition. On the contrary, in the fifth chapter regarding Tisha B'Av, he wrote that its bein hashemashot is forbidden, from which it is explicitly explained that in other fasts all of bein hashemashot is permitted. And so it is explained to me from the words of the Ran, that this matter of "all that the sun did not set upon" is according to its plain meaning, the setting of the sun. And if it is difficult: what is this coming to teach us? However, this refers back to the previous matter of whether one fasts for hours, see there. And upon this it says that any [fast] where the sun did not set—it is not a fast, meaning: and there is no fasting for hours. Therefore, when the Rambam wrote the law of a fast of hours, he did not need to mention this. And so it is explained from the words of Rashi, see there. And according to this, it appears in my humble opinion that one who relies on these, our teachers, to fast only until bein hashemashot—we do not cast him away. (And also the Gra in subsection 2 wrote so, and brought proof from the language of "his doubt" in the Gemara there. And also the Tosafot in Avodah Zarah 34a, starting with the words "Matunin," wrote as well that this setting of the sun is according to its plain meaning, see there. And I wonder that he did not bring proof from the Rambam, Rashi, and the Ran that we explained. And I saw the Korban Netanel in Shabbat there, who wanted to turn the intention of the Rosh to where he stipulated so explicitly, see there in letter 44, and his words are astonishing. And examine and you will find it easy.)

And behold, our teacher, the Rema, in section 1 wrote regarding the words of our teacher, the Beit Yosef—that anyone who did not fast until the emergence of the stars has not performed a fast—he wrote, and this is his wording: However, it is the custom to pray "Aneinu" even though they do not complete it until the emergence of the stars, and such is the opinion of some of the great authorities. And it seems to me that this is specifically for an individual who says "Aneinu" in "Shomea Tefillah," for in any case he may add [supplications], as I wrote in siman 119. But the shaliach tzibbur should not say "Aneinu" unless they complete it, and such is the custom. Thus far his words. And there are some of the commentators on the Shulchan Aruch who explained his intent in what he wrote, "and such is the opinion of some of the great authorities," that his intent was regarding the Rambam, who ruled on the matter of those who fast for hours according to its plain meaning, even though he ate on that day, as will be explained. And according to this, the intent of our teacher, the Rema, is that he may pray "Aneinu" even several hours before the night. And according to this, he wondered about him: for behold, this opinion is a rejected opinion. And furthermore: how can he say "the day of our fast" – for it is not a complete day? Therefore, he rejected his words (Turei Zahav, subsection 1). And there is one who explained his intent: when he specified at the time of acceptance not to complete it, for then even if he prayed Mincha Gedolah – he prays "Aneinu" (Magen Avraham, subsection 2). (And see in section 28 that even according to the Rambam there is no "Aneinu" in such a case.)

And all this is puzzling in my eyes. It is clear in his intent that it refers only to the emergence of the stars, meaning that even if they only fasted until sunset and not until the emergence of the stars—it is a fast and one prays "Anenu." And the "some authorities" are our teacher Yonah in the Rosh at the end of the second chapter of Shabbat, and the Tosafot there. And he wrote that in a community, the shaliach tzibbur should not say "Anenu," since it is a blessing unto itself, and the majority of opinions hold it must be until the emergence of the stars. And it appears in my humble opinion, that according to what we explained, that the opinion of the Rambam, Rashi, and the Ran is also such—even in a community they may rely on all these authorities. (And that which the annotators of the Rema wrote, that his source is from the Terumat HaDeshen, is an error, for it is not found there at all, see there.)

Our teacher, the Beit Yosef, wrote in section 2: And some say that one who is accustomed to fasting the Ten Days of Repentance, since it is not the custom to accept them during prayer—he does not need to fast until the emergence of the stars, but rather until he leaves the synagogue. Thus far his words. And our teacher, the Rema, wrote: And the individual prays "Anenu," and similarly a groom shall pray "Anenu" before he enters the chuppah, and then he may drink from the cup of blessing. But one who fasts from the seventeenth of Tammuz until the ninth of Av—he must complete the fast, even though it does not require acceptance. One who does not fast all of the Ten Days of Repentance, but only a day or two—requires acceptance and completion. And it seems to me that this is specifically when left unspecified, but if he made a condition not to complete it—he has the permission to do so, for it is no more stringent than any other fast. Thus far his words.

The explanation of the matters is that in Taanit (12a) it is stated: Any fast upon which the sun did not set is not called a fast. And it asks from the men of the watch, who would fast but not complete it. And it answers: There, it is merely to afflict themselves. Rashi explained: But it is not a fast, neither for the prayer of "Anenu" nor to establish it upon himself as an obligation at all. And any hour that he wishes to eat, he eats. Thus far his words. According to this, it is not in the category of a fast at all, and he may eat in the middle of the day whenever he wishes. And according to this, also during the Ten Days of Repentance, which is also merely to afflict oneself for atonement for his sins, so that his prayer will be accepted and his decree torn, and he does not accept it upon himself from yesterday at the time of Mincha—it is not in the category of a fast at all, and he eats whenever he wishes even in the middle of the day. And just as even now there are those who fast until after midday, and pray Mincha Gedola, and eat. And he does not say "Anenu," because it is not in the category of a fast at all.

But the Tur wrote, and this is his wording: Avi HaEzri wrote: One who is accustomed to fasting during the ten days of repentance—he does not need to fast the ten days until the emergence of the stars, but only until he leaves the beit knesset. For he accepted upon himself mere distress, as the Talmud challenges Rava Chisda from the men of the watch, who would fast and not complete it. And it answers there: For mere distress. And Rav Chisda only spoke of one who explicitly accepted a fast upon himself. And an unspecified fast is a full day, but during the ten days of repentance, it is not. And it is not the custom to accept it during prayer during the ten days of repentance. Thus far his words, and this is the opinion of the "there are those who say" in the Shulchan Aruch. And he disagrees with Rashi who wrote that he may eat whenever he wishes, for he required fasting until his departure from the beit knesset. And he calls this a fast, except that it is not required until the emergence of the stars. And since it is a fast, it follows that he prays "Aneinu" according to the words of our teacher, the Rema. And so it is in the Mordechai and in the Hagahot Asheri, and not like the words of Rashi that he does not pray "Aneinu."

And according to my humble opinion, they are following their own reasoning. For behold, we have already explained that Rashi, of blessed memory, holds that regarding any fast where the sun has not set upon it, this is not tzeit hakochavim but the sunset alone. And if so, consequently, that which they said, "they fast and do not complete it"—this means even before sunset. And if so, there is no limit to the matter, and even in the middle of the day, and consequently this is not in the category of a fast at all. But the Tur and the Avi HaEzri hold that regarding any fast where the sun has not set upon it—this is tzeit hakochavim, as the Tur wrote, see there; and so wrote the Mordechai in the name of the Ra'avyah, and he is the Avi HaEzri as is known. And according to this, that which they said, "they fast and do not complete it"—this is until tzeit hakochavim. But nevertheless, there must be some limit to the fast: either sunset, or after the congregation prays Arvit, which is from plag hamincha, an hour and a quarter before night. And this is what it says: until they exit the beit knesset (and so wrote the Magen Avraham, subsection 5). And since there is a limit to this, such that beforehand it is forbidden to eat—it follows that he prays "Aneinu."

According to this, the explanation of the words of our teachers, the authors of the Shulchan Aruch, is as follows: That one who accepts a fast in a literal sense—it is obvious that he must fast until the emergence of the stars, for such is the opinion of most posikim, even according to our teacher, the Rema, as I wrote in section 11. However, the fasts that are accepted and established by force of custom, such as the Ten Days of Repentance, or some days of them if they are only accustomed to fast on them consistently, such as those who fast on the first day of Selichot or the eve of Rosh Hashanah, which are without acceptance—granted that they are called a "fast" regarding the matter of "Aneinu," nevertheless, one does not need completion until the emergence of the stars; rather, it is sufficient until sunset or until after the evening prayer. For since there is a limit to this, that previously it was forbidden to eat—it is called a "fast." And so too a groom on his wedding day, who must fast until after the chuppah and that is his limit, and therefore he shall pray "Aneinu" before the chuppah, and then he may drink from the cup of blessing. But those who fast from the seventeenth of Tammuz until the ninth of Av—even without acceptance they must complete until the emergence of the stars, since their fast is over the destruction, it is automatically like the seventeenth of Tammuz and the ninth of Av. And so too during the Ten Days of Repentance, those who do not always fast equally, only a day or two, and not with a fixed schedule for this day or these two days, but rather once this day and once that day—it is obvious that it requires acceptance and completion. And if he accepted a fast without specification—he must complete until the emergence of the stars. However, if he made a condition at the time of accepting the fast not to complete—it is obvious that the authority is in his hand, and he does not need to complete. (This is the explanation of the words of the Shulchan Aruch. And so it appears that the Taz and the Magen Avraham understood, except that they were brief in the essence of the matters. And the words of the Bach in this matter require great study, see there. And the Rema, even though in the previous section he wrote that we are accustomed even in a complete fast not to fast until the emergence of the stars, yet here there is a novelty that even until sunset is not required, but rather until some limit, such as during the Ten Days of Repentance until after the evening prayer, and the groom until after the chuppah, and similar to this. And that which the Magen Avraham explained in subsection 6, and the Taz in subsection 3, to distinguish between the Ten Days of Repentance and between the straits [Bein HaMetzarim], because the Ten Days of Repentance the fast is for the future, and between the straits it is for the past over the destruction—it is a difficult concept. And their words are from the Terumat HaDeshen, and the Bach complained about this, and raised a powerful difficulty from that of Rabbi Eliezer son of Rabbi Tzadok who did not complete, and he fasted for the past. And the Taz and the Magen Avraham were pressed to answer, see there. But according to what I wrote this is not the essence, and it is merely an example. And the main reason is that since they are between the seventeenth of Tammuz and the ninth of Av, and the fast has one intention for them over the destruction—if so, it follows automatically that they complete until the emergence of the stars like they themselves. Which is not the case in that of Rabbi Eliezer son of Rabbi Tzadok, for on the ninth of Av itself he would not complete. And according to this, there is no starting point for the difficulty of the Bach. The general rule of the matter: all types of fasts that are without acceptance—one does not need to complete until the emergence of the stars, but rather until some limit. And so too those who fast from Rosh Chodesh Elul. Except for between the straits, for the reason we explained with the help of Heaven. And be precise and you will find it easy.)

An individual who accepted upon himself a fast without specification to fast on Erev Shabbat—he must fast until the emergence of the stars, unless he specified at the time of accepting the fast "until the congregation completes their prayer." And see above, siman 249. And similarly a fast for a dream—he must fast until the emergence of the stars, and even on Erev Shabbat, for since the remedy for a bad dream is the fast, as they said in Shabbat (11a)—a fast is as effective for a dream as fire is for flax. Consequently, a complete fast is required. And see above, siman 249.

Any individual fast that one did not accept while it was still day—it is not a fast, and he does not pray "Aneinu." And so too, if he is obligated in a certain fast—he does not fulfill his obligation with this fast to be exempt from his vow. Nevertheless, he is obligated to complete it, when it was in his mind to fast and to complete. And he also has a reward, and it is an atonement for sin, for it is no worse than one who afflicts himself from meat and wine. (And in the Magen Avraham, subsection 9, there is a printing error, and thus it must be said: if he began to fast on this day with the intent to complete, see there. And the Machatzit HaShekel was pressed regarding this, and there is no reason in his words there, see there. And even though at the beginning of siman 563 the Magen Avraham wrote that without acceptance at Mincha he does not need to fast at all, yet afterward he concludes that one should be stringent, see there. And the intention here is that he accepted it with his mouth, but not at its time.)

And know that in the Gemara there (10a) it is stated, Shmuel said: Any fast that one did not accept upon himself while it was still day—it is not called a fast. And if he sat [fasting], what is it? Rabba bar Shila said: It is like a bellows full of air. Rashi explained: It is a blacksmith's bellows that is filled with wind; so too this person is filled with wind, for he refrained from eating for nothing. Thus far his words. From this it is clear that he may eat even if he accepted upon himself to fast, since he did not accept it while it was still day. And so wrote the Mordechai there, and this is his wording: "Any fast..."—this implies that it is not considered a fast, and it is permitted to eat even though he accepted upon himself after dark to fast the whole day. For since he did not accept it while it was still day—it is as if he did not accept it. Thus far his words. And behold, all the poskim left their words unspecified, and wrote only the language of the Shas. But regarding our teacher, the Rema, it is a cause for wonder, for he wrote in section 5 on the words of the author—who wrote according to the language of the Shas that it is not a fast—he wrote and this is his wording: That it is not a fast to pray "Anenu," but not regarding the matter of whether he is obligated to fast... he has not fulfilled his vow... Thus far his words. And why did he not also write that it is permitted for him to eat? And one of the commentators on the Shulchan Aruch (Magen Avraham, subsection 9) wrote explicitly to the contrary, that he must pay his vow, meaning: and he is obligated to fast, as we wrote in the previous section. And this is against the words of Rashi and the Mordechai.

And it appears in my humble opinion that our teacher, the Rema, intentionally omitted this. For behold, there is indeed one who raised a difficulty: how is it permitted to eat, for in any event it is a vow (Magen Avraham at the beginning of siman 563 in the name of the Bach)? And they answered that a fast is one thing and a vow is another (ibid.). And this is based on the foundation that we explained in section 5 in the name of the Ramban, and the Ra'avad, and the Ritva, and the Nimukei Yosef, see there. And we have already written there that the opinion of the Rambam is not so, and we dealt with this at length in Yoreh Deah siman 215 with the help of Heaven, see there. And according to this, in the opinion of the Rambam, it is certainly forbidden to eat because of his vow, but regarding the fast, it does not count for him. And that which the Gemara asked: "And if he sat [fasted], what [is the law]?" – the intention is not that if he wishes he may eat, but rather this is the explanation: "And if he sat, what," meaning perhaps after the fact it counts for him as a fast? And it says that it is not so, but rather it is like a bellows full of air, meaning regarding the matter of the fast: that he does not pray "Anenu," and it also does not count as a fast, for he is obligated to pay it back. And therefore our teacher, the Rema, did not want to write explicitly that it is forbidden for him to eat, because according to most opinions it is permitted to eat. And he also did not want to write that it is permitted to eat, because it is against the opinion of the Rambam, and therefore he left the matters unspecified. (And the Magen Avraham here and at the beginning of siman 563, who wrote that it appears one should be stringent – it is either because he holds like the Rambam, or that he did not descend to the count [of opinions]. And we in the previous section wrote that he is obligated to fast, because the words of the Rema lean that way. However, for the law: one who does not want to fast and [wishes] to rely on the majority of the poskim – the authority is in his hand. And be precise and you will find it light.)

Our teacher, the Rema, further wrote: However, there are those who say that one prays "Anenu." And so it appears to me to practice in an individual fast. And according to everyone, in a fast for a dream one prays "Anenu," even though he did not accept it upon himself from yesterday. Thus far his words. And behold, in a fast for a dream it is certainly so, since the sages said that he should fast—it does not require his acceptance. But in an individual fast there is a dispute in the Mordekhai that we cited, and this is his wording there: However, it appears to the Ri that one prays "Anenu," for it is no worse than a fast for a dream. And the Raviah disagrees with him on this. And the Rabbi, the Mordekhai, heard from the mouth of our teacher, of blessed memory, that if he did not accept it while it was still day—he does not pray "Anenu" the next day. Thus far his words. And the comparison to a fast for a dream is not understood. However, their intention is that it is no worse than a fast of hours where one prays "Anenu," as will be explained. And that which he compares it to a fast for a dream, this is its explanation: just as in a fast for a dream one says "Anenu" without an acceptance from yesterday, so too here. For regarding an individual, since he does not establish a blessing for himself—we are not so particular, since in any event he accepted it. But when he did not accept it at all, but rather merely did not eat all day—it is nothing, and he does not pray "Anenu."

When does one accept it? During the Mincha prayer in "Shome'a Tefilla," or after he has finished his prayer before he uproots his feet. And he says: "Behold I am in a private fast tomorrow. May it be Your will that my prayer on my fast day be accepted." And if he did not express it with his mouth, but rather meditated in his heart that he accepts upon himself a fast for tomorrow – it is an acceptance. For this is like terumah and consecrated items where the conclusion in his heart suffices, even though he did not express it with his lips, as it is brought in Shevuot (26b). And only regarding an oath do we require expression with the lips. And specifically that he meditates so during the Mincha prayer, and accepted a complete acceptance in his heart to fast. But if he did not accept a complete acceptance, but rather his intention was to fast – it is nothing. And know that it is not specifically during the Mincha prayer, for that is only ab initio. But ex post facto – acceptance is effective as long as it is day, even after the Mincha prayer (Magen Avraham, subsection 12). And it is better to accept it after the prayer before he has uprooted his feet than during the prayer, so that he does not interrupt his prayer. Nevertheless, he should meditate in his heart also in "Shome'a Tefilla." And one should not say: Behold, regarding vows we hold in Yoreh De'ah siman 210 that acceptance in the heart is not effective just like an oath, so why is it effective regarding a fast? For it can be said that a fast is like a sacrifice, as he offers his fat and his blood which are diminished because of the weakness of the fast (Eliyah Rabbah, and so wrote the Taz in subsection 8).

The acceptance of the fast during the time of Mincha is effective even when one interrupts with eating, for behold, he eats and drinks the entire night. And likewise, it is effective even for several days, such as when he accepts on Sunday at Mincha that he will fast Monday, Tuesday, and Wednesday—it is a valid acceptance for all the days, even though he eats and drinks between them. And he does not require another acceptance, nor does he need to accept each one during the Mincha preceding it; the acceptance at Mincha that he accepted on Sunday for all the days is sufficient. And even if he said that he accepts upon himself two consecutive days—the intention is not consecutive without an interruption of eating at night between them, but rather the intention is that he will fast tomorrow until nightfall, and also the day following it, unless he explicitly specified that his intention was truly consecutive, without interruption during the nights. And regarding the matter of "Aneinu" in Mincha—there is no difference between one who only fasts during the day and not at night, and one who does not interrupt with eating during the nights.

And this is when the days for which he accepts the fasts are consecutive. However, if he accepted days that are not consecutive, such as if he accepted upon himself during the mincha prayer to fast four or five scattered days, like Monday and Thursday over two or three weeks and the like—there is one who is uncertain if one acceptance suffices for all of them, or if he requires an acceptance for each and every one. Nevertheless, the people are accustomed to accept them with one acceptance, and this suffices, and such is the opinion of some of the great authorities. And this is our custom regarding the fasts of Behab, that we accept on Shabbat for all three scattered days. But from this there is no proof, as this is like a communal acceptance. And the proof is: for behold, he does not require an acceptance during the preceding mincha, as I wrote in section 32.

And if he took upon himself to fast two consecutive days literally, including the night between them, and his heart grew weak and he ate during the night between them—he has lost his fast, and he does not pray "Aneinu," and he must complete other days (see Taz in the name of Kolbo). But one who took upon himself to fast many days with the interruption of the night between them, meaning that every night he would eat, and he fasted some days, and afterward did not fast on one of the days; nevertheless, when he fasts the days afterward, he says "Aneinu" on each day, because each and every day is a fast unto itself (ibid.).

And all this is when he accepted upon himself for several days. But if he accepted a ta'anit for only one day, such as if he said, "Behold, I am in a ta'anit tomorrow" and fasted, but on the night after the ta'anit he changed his mind to fast also tomorrow, and even if he slept in his ta'anit such that he did not eat at night and fasted also tomorrow on the second day—nevertheless, it is not a ta'anit, even though it continued together with the first day, since there was no kabbalah for the second day. And even if he accepted it on the second night—it is nothing. And it is worse than a ta'anit of hours, where he accepted them before the hours. And so too for a ta'anit of a full day—he must begin before the day. And nevertheless, he may pray "Anenu," for in any event it is like a ta'anit of hours, as I wrote in section 21, for he accepted it before he began to fast on the second day. And granted that it is not a day's ta'anit, nevertheless it is no worse than a ta'anit of hours (see Magen Avraham, subsection 15).

It was ruled in the Gemara (11b): The halakha is that one may fast for hours, and one prays the prayer of a fast. And this is provided that he did not taste anything the entire day. The explanation of these matters: for example, if one was busy with his affairs or his desires, and did not eat until midday or until nine hours, and he decided to fast during the hours that remained of the day – behold, he fasts those hours, and he prays "Aneinu" during them, for he accepted the fast upon himself prior to the hours of the fast. And this is not similar to what has been explained, that if he did not accept it during the Mincha prayer it is not a fast even if he accepted it at night. For is an acceptance at night worse than an acceptance the next day after midday? Certainly it is worse, because every type of fast must be accepted prior to the time that the fast takes effect upon him. Therefore, if his desire is to fast the entire day – he must accept the fast upon himself before the day takes effect, and the taking effect of the day is from the beginning of the night. And even though he eats at night – nevertheless, since this fast is considered a fast for the day, and the day follows the night, therefore he must accept it before the night. But in a fast of hours, he must accept it before the hours of the fast take effect. Therefore, when it entered his mind to fast such and such hours, and he accepted them before the hours – it is a proper acceptance. However, the condition for this is that he did not eat beforehand as well due to a mere reason, as I have written. For if not so, how is this called a fast? Behold, he did not fast.

And it is true that the approach of the Yerushalmi is that even if one ate on that day, and afterward it entered his mind to fast the remainder of the day—it is also called a fast of hours. And so wrote the Rambam in the first chapter, see there. But they have already raised a difficulty against him: Behold, the approach of our Shas is not so? And the Rambam adopted both: like the approach of our Shas and like the approach of the Yerushalmi. And in my humble opinion, it appears that the law is with the Rambam, for the Shas which requires that he not eat the entire day—this is regarding the prayer of "Aneinu." For if not so, how could he say "Answer us on the day of our fast" since he did not fast? But nevertheless, even the Shas admits that it is considered a fast of hours, and he has a reward, and it is forbidden to eat during these hours. However, he does not pray "Aneinu" (the Yerushalmi is in the eighth chapter of Nedarim).

This is the wording of the Rambam there, law 13: A person may fast for hours, provided that he does not eat anything for the rest of the day. How so? If one was occupied... — he fasts those hours and prays "Anenu" during them... And likewise, if he ate and drank and afterwards began to fast for the rest of the day — this is a fast of hours. Thus far his words, and he did not conclude that he should pray "Anenu" because in such a case it is not necessary, and it is impossible to pray "Anenu." And he holds that that which the Shas says, "provided that he did not taste anything the entire day" — refers to that which it said, "and he prays the prayer of the fast" (so it appears to my humble opinion clearly). And know that in Rashi there it is explained that if he accepted upon himself while it was yet day to fast the next day until midday, and afterwards he decided not to eat until night — it is a complete fast and not a fast of hours. See there.

And behold, the Tur and the Shulchan Aruch also wrote in section 11, and this is their wording: If he accepted upon himself a fast until midday and ate afterwards, or if he ate until midday and accepted upon himself a fast from then onwards – it is not called a fast for the purpose of praying "Anenu." However, it is called a fast regarding the matter that he must fulfill his vow. Thus far their words. And according to this, I am greatly wondered at the Tur and the Maggid Mishneh, and others of the poskim who rejected the words of the Rambam, and wrote that it is an error. And that they heard that the Rambam himself recanted (see Beit Yosef). And it is a great wonder: for the Rambam also says so, and behold the precision of his pure wording indicates so, for previously he wrote that one says "Anenu" and afterwards he did not write so. And it requires great study.

However, according to the opinion of the Rosh and the Tur, what we wrote—that one did not eat until midday—is not a ta'anit sha'ot; rather, even a ta'anit sha'ot must be accepted from the previous day. This means, for example, that he accepted from the previous day to fast until midday, and afterward he decided not to eat until nightfall, or that he took upon himself from the previous day to fast the next day from midday onward, and afterward he decided not to eat even until midday—for this is called a ta'anit sha'ot. But according to Rashi, of blessed memory, this is a complete fast, as I wrote in section 29. And according to this, in the opinion of the Rosh and the Tur, anything without an acceptance while it was still day is not a fast at all regarding the matter of "Aneinu." And according to this, all the details we wrote previously, that their law is that if he accepted at night he must pray "Aneinu," as it is no worse than a ta'anit sha'ot—according to the opinion of the Rosh and the Tur, it is not so.

A fast that is decreed upon the community – no individual needs to accept it during the mincha prayer; rather, the shaliach tzibbur announces the fast – and it is thereby accepted. And some say that these words apply in Eretz Yisrael, for they had a Nasi since his decree was binding upon all of Israel. But in the diaspora – the entire community must accept it upon themselves as individuals, such that each one accepts it upon himself. And it appears to me that in any case, even in such a manner, their law is not like an individual who must accept it during the mincha prayer; rather, whenever they accept it, it is a fast, because when a community accepts together, even though each one accepts for himself – they are like a great beit din. As I wrote in Choshen Mishpat siman 2, that the city leaders in their city are likened to a great beit din. And all the more so the entire community together. And a proof for this is from the fasts of Behab, where the shaliach tzibbur announces during shacharit, and the community answers "Amen," and they do not require any other acceptance. (And with this, the difficulty of the Taz, subsection 16, is resolved. And regarding what he wrote that an individual who accepted a fast by a vow is obligated from the Torah to fast, see there – he did not set his pure heart to the fact that a fast is not a vow from the Torah, as I wrote above. Examine carefully and you will find it simple.)

Our teacher, the Beit Yosef, wrote in section 13: There is one who says that one who vowed and said, "If I do not go to such-and-such a place, I shall sit in a fast," since that which he stipulated is a discretionary matter—it is an asmachta. But if he said, "If I do not perform such-and-such a mitzvah, I shall sit in a fast," and likewise if he said, "If Hashem saves me from trouble or if He makes my path successful"—it is not an asmachta. Thus far his words, meaning: for we hold in Choshen Mishpat siman 207 that an asmachta does not effect a legal acquisition. And this is when he said, "If it will be so," for every "if" is an asmachta, and he did not resolve in his heart to truly do so. However, regarding a matter of a mitzvah, it is explained there that there is no asmachta, for regarding any matter of a mitzvah, he resolves in his heart completely. And it is an explicit verse regarding Yaakov (Genesis 28:20): "If G-d will be with me and protect me...". And with this, the matters are explained: "And if He makes my path successful" is also in this regard like a matter of a mitzvah, for in the merit of the success, he resolves and grants (Magen Avraham subsection 17). Nevertheless, there is room to question this: for granted that the condition was regarding a discretionary matter, nevertheless, since he said "I shall sit in a fast"—behold, it is a matter of a mitzvah, and let it not be an asmachta just as regarding tzedakah in Yoreh Deah siman 258, where it is not an asmachta in such a case, see there. And it must be said that he holds that a fast itself is not called a matter of a mitzvah, for behold, in the Gemara there is one who holds that one who sits in a fast is called a sinner. Therefore, he wrote in the name of "there is one who says," meaning: but one who holds that in all matters a fast is like tzedakah—even in a discretionary matter there is no asmachta. (And with this, the difficulties of the Taz subsection 17 and the Magen Avraham subsection 16 are settled, see there. And examine carefully and you will find it simple.)