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(1) It is an affirmative precept of the Torah to say Grace after a meal, as it is said, "And thou shalt eat and be satisfied and shalt bless the Lord, thy God" (Deuteronomy 8:10). The Torah only imposes the obligation on a person when he is satisfied; for it is said, "When thou hast eaten and art satisfied, thou shalt bless etc." According to the ordinances of the sages, however, even if one has eaten only as much food as the size of an olive, he recites Grace after the meal.

(10) When you have eaten your fill, give thanks to the LORD your God for the good land which He has given you.

After citing the halakha that one who eats a quantity of food that does not satisfy his hunger is obligated by rabbinic law to recite Grace after Meals, the Gemara cites a related homiletic interpretation. Rav Avira taught, sometimes he said it in the name of Rabbi Ami, and sometimes he said it in the name of Rabbi Asi: The ministering angels said before the Holy One, Blessed be He: Master of the Universe, in Your Torah it is written: “The great, mighty and awesome God who favors no one and takes no bribe” (Deuteronomy 10:17), yet You, nevertheless, show favor to Israel, as it is written: “The Lord shall show favor to you and give you peace” (Numbers 6:26). He replied to them: And how can I not show favor to Israel, as I wrote for them in the Torah: “And you shall eat and be satisfied, and bless the Lord your God” (Deuteronomy 8:10), meaning that there is no obligation to bless the Lord until one is satiated; yet they are exacting with themselves to recite Grace after Meals even if they have eaten as much as an olive-bulk or an egg-bulk. Since they go beyond the requirements of the law, they are worthy of favor.

Women, slaves, and minors do not obligate those with whom they ate in a zimmun.How much must one eat to obligate those with whom he ate in a zimmun? An olive-bulk of food suffices to obligate those with whom they ate in a zimmun. Rabbi Yehuda says: An egg-bulk is the minimum measure to obligate those with whom they ate in a zimmun.

(15) If two persons had their meals together, each of them says Grace for himself. If one knew the Grace while the other did not know it, the former recites it aloud and the latter responds "Amen" after each blessing and thus fulfills his duty. A son may in this way recite Grace on his father's behalf; a slave for his master; a wife for her husband. But the sages say "A curse will befall one whose wife or child recites the Grace for him."

(16) It is however to be noted that these persons are only discharged of their obligation if they partook of a meal and their hunger is not satisfied. In this case the obligation to say Grace is one imposed by the dicta of the Scribes, and can therefore be fulfilled on their behalf by a minor, slave or woman. But if one has eaten and is satisfied, the duty to say Grace is Scriptural and cannot be discharged on his behalf by a woman, minor or slave, on the principle that anyone who is under an obligation imposed by the Torah can only be discharged of it by one upon whom the Torah imposes the same obligation.

One Sage teaches that this ritual impurity applies to meat in the amount of an olive-bulk, and the other Sage teaches that the minimum amount of meat necessary for the decree to apply is an egg-bulk. The Gemara explains: The reason for the one who teaches that the minimum amount of meat necessary for the decree to apply is an olive-bulk is that the decree is like its prohibition; one violates the prohibition to eat piggul or leftover sacrificial meat only when one eats an olive-bulk. And the one who teaches that the decree applies only when there is an egg-bulk of meat reasons that it is like its ritual impurity; by Torah law, only an egg-bulk of food can impart ritual impurity.