Rif Brachot 33a

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33a

{Brachot 45a continued}
OR SANCTIFIED FOOD WHICH HAS NOT BEEN REDEEMED, OR AN ATTENDANT WHO HAS EATEN LESS THAN THE QUANTITY OF AN OLIVE OR A GENTILE MAY NOT BE COUNTED.
WOMEN, CHILDREN AND SLAVES MAY NOT BE COUNTED IN THE THREE.
HOW MUCH [MUST ONE HAVE EATEN] TO COUNT? AS MUCH AS AN OLIVE; R. JUDAH SAYS, AS MUCH AS AN EGG.

Gemara:
How do we know this? {to join together}
Rav Asi said: For Scriptures state {Tehillim 34:4}

ד גַּדְּלוּ לַה אִתִּי; וּנְרוֹמְמָה שְׁמוֹ יַחְדָּו.

4 O magnify the LORD with me, and let us exalt His name together.

Rav Chanin bar Avin said: How do we know that one who answers Amen should not raise his voice louder than he who said the blessing? For it is stated {Tehillim 34:4}:

ד גַּדְּלוּ לַה אִתִּי; וּנְרוֹמְמָה שְׁמוֹ יַחְדָּו.

4 O magnify the LORD with me, and let us exalt His name together.

{Brachot 45b}
Abaye said: We have a tradition that two people who have eaten, it is a mitzvah to separate {and say Birchat HaMazon}.

A brayta also says so: Two who have eaten, it is a mitzvah to separate.

When are these words said? When they are both sofrim {educated people}, but if one is educated and the other is uneducated, the educated one blesses and the uneducated one thereby fulfills {his obligation}.

Rav Dimi bar Yosef cited Rav: Three who ate, and one of them went out to the shuk, they call to him, and count him for the zimmun.

Abaye said: and that is where they call to him and he answers.

Mar Zutra said: They only said this is regards to three, but ten, they must wait unitl he returns.

Three who are eating together, one breaks off {eating} for {the other} two, but two do not break off for one.

Yehuda bar Mereimar, Mar bar (*Rav) Ashi, and Rav Acha MiDifti consumed flat cakes together. They said: this that we learned {in the Mishna} that three who have eaten together are obligated to make a zimmun, these words were said where there is one who is superior {to the others}, but for us, splitting up the blessings {such that each says Birchat HaMazon individually} is better. Each one blessed for himself. They came before Mereimar. He said to them: in terms of the blessing you have fulfilled; in terms of the obligation of zimmun you have not fulfilled. And if you say, let us go make and make the zimmun, the zimmun cannot be said out of its place.

If he came and found them as they were blessing {Birchat HaMazon}, what should he answer after them?
Rav Zevid said: Baruch Umvorach {Blessed and to be blessed}.
And Rav Papa said: Amen.