Siman 186

Women are obligated in birkat hamazon, as it is a positive commandment not caused by time, for whenever one eats, one is obligated to bless. Nevertheless, it was a matter of doubt in the Gemara (20b) whether their obligation is from the Torah or only from the rabbis and they are exempt from the Torah, because it is written: "And you shall bless... for the good land..." – and women did not take a portion in the land (Rashi). And even though Kohanim and Levi'im also did not take a portion in the land, nevertheless they had the migratory cities. Furthermore, since they took terumot and ma'asrot from the produce of the land, they are as if they "have a portion in the land," which is not the case for women. Furthermore, since in the blessing of the land one is obligated to say "for Your covenant which You sealed in our flesh, and for Your Torah which You taught us," and women are in neither the covenant nor the Torah (Tosafot). And one cannot say: granted that they are exempt from the blessing of the land, but from the blessing of "Hazan" why should they be exempt? For first Moshe our teacher instituted the blessing of "Hazan" at the time the manna descended for them, and Yehoshua instituted the blessing of the land when they entered the land, and David and Shlomo instituted "Boneh Yerushalayim" (48b). And when Moshe instituted it – he certainly instituted it for women as well, for the manna descended for them too. If so, by what were they exempted afterwards? And likewise from "Boneh Yerushalayim," why are they exempt? For it can be said that since we derive from the verse "And you shall bless" – this is the blessing of "Hazan...", "for the land" – this is the blessing of the land, "the good" – this is Boneh Yerushalayim (ibid.). Therefore, anyone who is obligated in the blessing of the land is obligated in all of them, and anyone who is not obligated in the blessing of the land is exempt from all of them. Furthermore, because the obligation of sustenance for women is upon their husbands, for the man is obligated to sustain his wife. Therefore, even regarding the core of the blessing of "Hazan," it can be said that it does not pertain to them. Likewise, the building of Yerushalayim is primarily for men, and the women are secondary to the men (so it appears in my humble opinion).

And they said in the Gemara there that there is a practical difference whether their obligation is from the Torah or from the rabbis: for if it is from the Torah, they can fulfill the obligation for men, and if it is from the rabbis, they cannot fulfill it, for a rabbinic obligation does not come and fulfill a Torah obligation. And even though we hold that one who ate a kezayit of grain can fulfill the obligation for one who ate until satiety, even though from the Torah there is no obligation except until satiety, as it is written: "And you shall eat and be satisfied" – it is not comparable. Firstly, according to the opinion of the Ra'avad in the fifth chapter of Berakhot, they are obligated even from the Torah for a kezayit, see there. And even according to the opinion of the Rambam and the Tosafot that a kezayit is only from the rabbis, nevertheless, since the essence of his obligation is from the Torah, and in truth from the Torah he would have been able to fulfill the obligation for others even when he did not eat at all, like all blessings of the mitzvot where all Israel are guarantors; and it is not comparable to a blessing of enjoyment where he cannot fulfill the obligation for others when he himself is not enjoying, for a blessing of enjoyment is not obligatory. But Birkat HaMazon after eating is obligatory and is like the blessings of the mitzvot, except that from the rabbis they said that as long as he has not eaten a kezayit of grain – he cannot fulfill the obligation for others. And so it is explicitly stated in the Gemara. (48a; and Shimon ben Shatach held to compare it entirely to mitzvot, see there. And examine carefully and you will find it easy.) And therefore if he only ate a kezayit – he can fulfill the obligation for others, which is not the case for women if they are not obligated at all (Rashba ibid. 48a). And that which we say in the Yerushalmi, the third chapter of Berakhot, that Birkat HaMazon is not comparable to all the mitzvot, because it is written: "And you shall eat and be satisfied and you shall bless," he who ate shall bless – this is from the rabbis (ibid.). And the Tur brought the opinion of the Ri that in truth even one who did not eat can fulfill the obligation for others, see there. And this is the opinion of the Tosafot in Berakhot there (end of the comment starting "Ad"), and they wrote that this which we say in the Gemara that he must eat a kezayit of grain – this is regarding the matter of zimun, that he must say "of whose food we have eaten." But without zimun he can fulfill the obligation for others. And the Tur disagrees in this, see there. And thus we hold, for so it appears to be the opinion of most of the poskim. (And the opinion of the Rambam in the fifth chapter is that in truth one who ate only a kezayit cannot fulfill the obligation for one who ate until satiety. And so wrote the Rashba in the name of the Ba'al HaHalakhot, see there. And this is the opinion of the Behag, see there.)

The opinion of the Ra'avad and the Rashba is that the inquiry was resolved, and women are obligated in birkat hamazon by Torah law, and they can also discharge the obligation for men. Nevertheless, regarding zimun they do not join because of immodesty, and it will be explained in siman 199. However, the opinion of the Tosafot and the Rosh is that the inquiry was not resolved and it remains a legal doubt, and this is also the opinion of the Rambam in the fifth chapter, see there. Our teacher, the Beit Yosef, ruled accordingly in section 1. Therefore, they only discharge the obligation for one whose obligation is of rabbinic origin, such as a woman or a minor. And a slave's law is like that of a woman. And a tumtum and an androgyne are a doubt whether they are a man or a woman, and therefore a woman does not discharge their obligation, and they do not discharge the obligation for a man; and they also do not discharge the obligation for one another, for perhaps this one is male and that one is female. And there are some of the poskim for whom it is obvious that the conclusion of the sugya is that the obligation of women is only of rabbinic origin, and this is the opinion of our teacher Yonah (see Beit Yosef). And such is the opinion of the Zohar Terumah (168b), see there. (See Magen Avraham subsection 1.)

A minor, when he has reached the age of chinuch—the father is obligated to train him in birkat hamazon by rabbinic law. And he does not discharge the obligation for a woman according to the one who holds that her obligation is a doubt or a certainty from the Torah. And the minor's obligation in chinuch applies even when he has eaten only a kezayit, for whatever the sages ordained, they ordained similar to the Torah law (Eliyah Rabbah). And so too for women. And the minor does not discharge the obligation for an adult unless the adult ate only a kezayit, for his obligation is rabbinic; and so too a woman does not discharge the obligation for a man unless he ate only a kezayit. And this is what we learned in Sukkah (38a): A son recites the blessing for his father, and a woman for her husband, and a slave for his master; for since they ate to the point of satiety, and they have a rabbinic obligation—they discharge the obligation for men who ate only a kezayit, whose obligation is also rabbinic. And if they also ate only a kezayit—they do not discharge the obligation, for two rabbinic levels cannot come and discharge one rabbinic level (Tosafot at the end of the second chapter of Megillah 19b, starting with the words "And Rabbi Yehuda"). And there is one who hesitates regarding this (Magen Avraham, subsection 3). And also from the wording of the Rambam in the fifth chapter, law 16, it appears more like this opinion that there is no distinction, see there. And according to the opinion of the Ra'avad that a kezayit is an obligation from the Torah, in any case they are unable to discharge the obligation for adult men. And that which was said that a son recites the blessing for his father and a woman for her husband, the intention is not that they discharge their obligation, but rather that he answers after them what they say, and blesses for himself. And that which requires their reading is because he is not proficient. And therefore we indeed learned there: "May a curse come upon a man whose wife and sons recite the blessing for him," see there. (And daughters are not subject to chinuch for birkat hamazon.)