The Gemara recounts: Rabbi Zeira took ill. Rabbi Abbahu went to visit him and resolved: If the little man with the scorched legs, a nickname for Rabbi Zeira, is cured, I will make a festival, a feast, for the Sages. Rabbi Zeira was cured and Rabbi Abbahu made a feast for all the Sages. When it came time to break bread, Rabbi Abbahu said to Rabbi Zeira: Master, please break bread for us. Rabbi Zeira said to him: Doesn’t the Master hold in accordance with that halakha of Rabbi Yoḥanan, who said: The host breaks bread? Rabbi Abbahu broke bread for them.

When the time came to recite the blessing, Rabbi Abbahu said to Rabbi Zeira: Master, recite Grace after Meals on our behalf. Rabbi Zeira said to him: Doesn’t the Master hold in accordance with that halakha of Rabbi Huna of Babylonia, who said: He who breaks bread recites Grace after Meals?

The Gemara asks: And in accordance with whose opinion does Rabbi Abbahu hold that he asked Rabbi Zeira to recite Grace after Meals?

The Gemara answers: Rabbi Abbahu holds in accordance with that halakha that Rabbi Yoḥanan said in the name of Rabbi Shimon ben Yoḥai: The host breaks bread and a guest recites Grace after Meals. The host breaks bread so that he will break bread generously, whereas a guest might be embarrassed to break a large piece for himself and other guests; and the guest recites Grace after Meals so that he may bless the host in the course of reciting Grace after Meals, as the Gemara proceeds to explain.

What is the formula of the blessing with which the guest blesses his host?
May it be Your will that the master of the house shall not suffer shame in this world, nor humiliation in the World-to-Come.

Rabbi Yehuda HaNasi added to it elements pertaining to material success:
And may he be very successful with all his possessions,
and may his possessions and our possessions be successful and near the city,
and may Satan control neither his deeds nor our deeds,
and may no thought of sin, iniquity, or transgression stand before him or before us
from now and for evermore.

The Gemara asks: Until where does the zimmun blessing extend?

Rav Naḥman says: The blessing extends only until: Let us bless. Rav Sheshet says that the zimmun blessing extends until the end of the first blessing of Grace after Meals: Who feeds all.

The Gemara proposes: Let us say that this amoraic dispute is parallel to a dispute between the tanna’im. As one baraita taught: Grace after Meals is two and three blessings, and another baraita taught: Grace after Meals is three and four blessings. In attempting to understand these conflicting baraitot, the Sages assumed that everyone agrees that the blessing: Who is good and does good, the fourth blessing of Grace after Meals, is not required by Torah law. What then? Is it not that they disagree about this: The one who said that Grace after Meals is two and three blessings holds that the zimmun blessing extends until the end of the blessing: Who feeds all? If there is a zimmun, three blessings are recited; if there is no zimmun, only two blessings are recited, since the blessing: Who feeds all, is not recited. And the one who said that Grace after Meals is three and four blessings holds that the zimmun blessing extends only until: Let us bless, and includes no part of Grace after Meals itself. If there is a zimmun, four blessings are recited, the three blessing of Grace after Meals plus the blessing of the zimmun, while if there is not, only three blessings are recited.

This explanation distinguishing between the baraitot is rejected: No; Rav Naḥman explains in accordance with his reasoning and Rav Sheshet explains in accordance with his reasoning.

Rav Naḥman explains in accordance with his reasoning; everyone agrees that the zimmun blessing extends only until Let us bless. According to the one who said that Grace after Meals is three and four blessings, this works out well. And the one who said that Grace after Meals is two and three blessings could have said to you: Here we are dealing with the blessing recited by laborers, as the Master said that when a laborer is working, he is permitted to abridge Grace after Meals, and he begins with the blessing: Who feeds all, and includes the third blessing: Who builds Jerusalem, in the context of the second blessing, the blessing of the land.

Rav Sheshet explains in accordance with his reasoning; everyone agrees that the zimmun blessing extends until the end of the blessing: Who feeds all. According to the one who said that Grace after Meals is two and three blessings, this works out well; and the one who said that Grace after Meals is three and four blessings holds that the blessing: Who is good and does good, is required by Torah law.

With regard to the matter of the blessing: Who is good and does good, Rav Yosef said: Know that the blessing: Who is good and does good, is not required by Torah law, as laborers who recite Grace after Meals at work eliminate it. If it can be eliminated, it could not be a Torah obligation.

Rav Yitzḥak bar Shmuel bar Marta said another proof in the name of Rav: Know that the blessing: Who is good and does good, is not required by Torah law, as one who recites it begins to recite it with: Blessed, but does not conclude reciting it with: Blessed. This is the formula in all comparable blessings, as it was taught in a baraita: All blessings, one begins to recite them with: Blessed, and concludes reciting them with: Blessed, except for blessings over fruit, blessings over mitzvot, a blessing that is juxtaposed to another blessing, and the final blessing after Shema. There are among these blessings those that one who recites it begins to recite it with: Blessed, but does not conclude reciting it with: Blessed;