Siman 580

The Geonim wrote that these are days upon which one fasts because troubles befell our ancestors on them, and it is fitting to fast on them. And even though some of them fall on Rosh Chodesh, there is one who says that one should fast on it. This is a wondrous thing, and the Geonim themselves responded not to fast on Rosh Chodesh (Beit Yosef and Magen Avraham), and therefore it is good not to complete the fast. In Worms they used to fast on Rosh Chodesh Sivan because of the decrees (Beit Yosef in the previous siman in the name of the Rokeach), but we do not learn from them (Magen Avraham in siman 572 in the name of the Rama Mi-Pano). And I believe I saw that they pray Mincha at the third hour after midday and eat. However, now in our time and in our country, we have not heard of anyone who fasts on these fasts that will be explained. For the decree was not from the Geonim to fast on them, but rather they wrote that it is fitting to fast on them. Furthermore: after the sealing of the Talmud, there is no power to decree upon all of Israel. And the Tur brought in the name of the Ba'al HaHalachot Gedolot in this wording: These are the days that one fasts on them from the Torah, see there. And the wording is very puzzling (see Beit Yosef and Bach), and it requires further study.

And these are the days: On the first of Nisan, the sons of Aharon died. On the tenth of it, Miriam died, and the well departed. On the twenty-sixth of it, Yehoshua bin Nun died. On the tenth of Iyar, Eli the Kohen and his two sons died, and the Ark of Hashem was captured. On the twenty-eighth of it, Shmuel the Prophet died, and some say on the twenty-ninth of it (Magen Avraham in the name of Megillat Taanit). On the twenty-third of Sivan, the bikkurim were prevented from being brought up to Yerushalayim in the days of Yerovam ben Nevat. On the twenty-fifth of it, Rabban Shimon ben Gamliel, Rabbi Yishmael, and Rabbi Chanina Segan HaKohanim were killed. On the twenty-seventh of it, Rabbi Chananya ben Teradyon was burned and a Sefer Torah with him. On the first of Av, Aharon the Kohen died. On the eighteenth of it, the western lamp was extinguished in the days of Achaz. On the seventeenth of Elul, those who brought forth an evil report of the Land died, and some say on the seventh of Elul (ibid.).

On the fifth of Tishrei, twenty men of Israel died, and Rava Akiva was imprisoned. On the seventh of it, a decree was issued against our ancestors that they should die by the sword, by famine, and by pestilence because of the incident of the Calf. And even though the Holy One, Blessed be He, was afterwards appeased, nevertheless the iniquity is preserved for generations. On the seventh of Marheshvan, the eyes of Zedekiah were blinded, and his sons were slaughtered before his eyes. And some say on the sixth of it (ibid.). On the twenty-eighth of Kislev, Jehoiakim burned the scroll that Baruch wrote from the mouth of Jeremiah. And some say on the seventh of Kislev, and some say on the eighth, and some say on the fifth (ibid.). Therefore, on the twenty-eighth one should not fast, as it is Hanukkah (ibid.). On the eighth of Tevet, the Torah was written in Greek in the days of King Ptolemy, and there was darkness in the world for three days. On the ninth of it, the trouble that occurred on it was not known, and it was revealed afterwards that on it Ezra the Scribe died. On the fifth of Shevat, the elders who were in the days of Joshua died, and some say on the eighth of it (ibid.). On the twenty-third of it, all Israel gathered against the tribe of Benjamin regarding the incident of the concubine in Gibeah. On the seventh of Adar, Moses our teacher, peace be upon him, died, and in a leap year it is in the first Adar (ibid.). On the ninth of it, the Beit Shammai and the Beit Hillel disagreed, and the matter was difficult for Israel, and they decreed a fast over this.

And there is one who says that they decreed that they should fast every Monday and Thursday over the destruction of the Temple, and over the Torah that was burned, and over the desecration of the Name. Furthermore, it is found in the early authorities that they decreed a fast on the eve of the holy Shabbat of Parshat "Chukat," for then in France they burned twenty wagons full of books. And they established it on the day of the week and not on the day of the month, for it was revealed to them in a dream that this is what Onkelos translated on "This is the statute of the Torah" – "This is the decree of the Torah." And the Rambam wrote at the end of the Laws of Fasts: All these fasts are destined to be nullified in the days of the Mashiach. And not only that, but they are destined to be festivals and days of joy and gladness, as it is said: "Thus says the Lord of Hosts: The fast of the fourth, and the fast of the fifth, and the fast of the seventh, and the fast of the tenth shall be to the house of Judah for joy and gladness and for good festivals." And love truth and peace. Amen and Amen. With the help of Heaven, the Laws of Fasts are completed.