Gemara

The Mishnah says that the Kohen who received the blood gave it to another Kohen. This teaches that Holachah without walking is considered Holachah.

Rejection: Perhaps he would move his feet a bit;

The Mishnah mentions this to teach that "b'Rav Am Hadras Melech." (It is more honorable when many engage in the Avodah.)

Berachos 43a (Mishnah): If they reclined, one blesses [Birkas ha'Mazon] for everyone.

Version #1 (Rav): Only bread requires reclining [for one to bless for everyone]. Wine does not require reclining.

(R. Yochanan): Even wine requires reclining.

Version #2 (Rav): Reclining helps only for bread, but not for wine;

(R. Yochanan): It helps even for wine.

45b (Abaye): The Halachah is, if two ate together, each should bless by himself.

Support (Beraisa): If two ate together, each should bless by himself;

This is if both are Chachamim. If one is a Chacham and the other an ignoramus, the ignoramus should be Yotzei through listening to the Chacham.

Chulin 106a (Rabah bar bar Chanah): I was in front of R. Ami and R. Asi. Peros were brought to them. They did not give to me. Each blessed by himself.

We learn from this that when people eat Peros together, they need not be Mezamen (have one bless to exempt the others). If two ate Peros, it is better for each to bless for himself, than for one to exempt the other.

Rishonim

Rambam (Hilchos Berachos 1:12): If many gathered to eat bread or drink wine, and one blessed and all answered Amen, they may eat and drink. If they did not intend to eat together, rather, each came by himself, even if they eat from one loaf, each blesses for himself. This refers only to bread and wine. Other food and drink does not need Haseivah (reclining together). Rather, if one blessed and all answered, they may eat and drink, even though they did not intend to recline together.

Kesef Mishneh: The Ramah argued, and said that it is more esteemed that one bless to exempt the Rabim. The Rambam rules like the first version to be lenient, for this matter is mid'Rabanan. Also the Ramach learns from Berachos 39a in which Bar Kapara authorized a Talmid to bless [a Berachah Rishonah on Peros] to exempt the others, and R. Gamliel did similarly [regarding a Berachah Acharonah - Berachos 37a]. One blesses for everyone, due to "B'Rav Am Hadras Melech." Also the Rif says so. In Chulin, each blesses for himself. They explain that this is only when there are only two people.

Rosh (Berachos 6:7): Abaye taught that if two ate together, the Mitzvah is to divide. Rashi says that this is both for Birkas ha'Mazon and ha'Motzi. The custom is unlike this. Also, we did not hear that Rashi himself did so regarding ha'Motzi. Bar Kapara told a Talmid to make a Berachah Rishonah for everyone. The difference between Berachah Rishonah and Acharonah is that at the start of the meal, when all are reclining and fixed together, they intend to join, so one is Yotzei through another's Berachah. At the end of the meal, their Kevi'us is Batel and they separate, so each blesses for himself. R. Yosef said in the name of the Rashbam that Birkas ha'Mazon is mid'Oraisa, but a Berachah Rishonah is only mid'Rabanan, so Chachamim were not stringent, and one is Yotzei through another. If one is a Chacham and the other is an ignoramus, the ignoramus is Yotzei through listening to the Chacham. Some derive that a woman is Yotzei through hearing Birkas ha'Mazon even if she does not understand Lashon ha'Kodesh. One need not bless for her in a language she understands. There is no proof from here. Perhaps the ignoramus understands Lashon ha'Kodesh, but does not know how to bless! Rashi brought a proof from Megilah 17a. If one who speaks [only] a foreign language heard the Megilah in Lashon ha'Kodesh, he was Yotzei. I reject the proof. Perhaps [Keri'as ha'Megilah, which is for the sake of] publicizing the miracle, is different. Ravina said that we do not know what are "ha'Achashteranim Bnei ha'Ramachim", [yet we are Yotzei], for publicizing the miracle is different.

Rosh (7:3): A waiter may eat without permission when he serves two, but not when he serves three. This implies that it is a Mitzvah to seek to bless with three for a Zimun, due to b'Rav Am Hadras Melech. We infer this also from Chulin 106a. They did not give to Rabah bar bar Chanah because there is no Mitzvah to be Mezamen on fruit. If it were a Mitzvah, they would have given to him.

Rosh (8:3): Beis Hillel say that [in Havdalah] one blesses on fire for everyone, due to b'Rav Am Hadras Melech. This is unlike bread (43a). There, everyone blesses for himself, for we require reclining together to be Yotzei [l'Chatchilah] through another.

Poskim

Shulchan Aruch (OC 193:1): If two ate together, even though one may exempt the other in Birkas ha'Motzi, the Mitzvah is to divide and each blesses Birkas ha'Mazon for himself.

Taz (1): Even according to the Rashbam, who says that Rabanan were not stringent about Berachah Rishonah because it is mid'Rabanan, we must separate for [even the Berachah Rishonah on] Peros, like it says in 213:1.

Kaf ha'Chayim (1): The primary opinion is that it depends on Kevi'us. If it depended on being mid'Rabanan, one would be able to be Motzi others l'Chatchilah also for Peros, even for a Berachah Acharonah. The Taz wrote according to the Rema. The Mechaber holds that Kevi'us for Peros helps for a Berachah Rishonah.

Mishnah Berurah (2): Even though b'Di'eved, surely even Birkas ha'Mazon one is Yotzei through another who is Motzi him, l'Chatchilah the Mitzvah is to divide. The Pri Megadim says that it is proper to be concerned for the Rosh's reason (that the Kevi'us ended). Even if one did not eat to satiation, and Birkas ha'Mazon is mid'Rabanan, the Mitzvah is to divide.

Shulchan Aruch (ibid.): This is if both know how to bless. If only one knows, he blesses and the other is Yotzei if he understands Lashon ha'Kodesh but does not know how to bless.

Taz (2): The Tur concludes that women who do not understand Lashon ha'Kodesh are not Yotzei through listening. The Beis Yosef brings from Rashi that they are Yotzei without understanding. Even though we do not hold like this, since our women do not understand Lashon ha'Kodesh, they should rely on Rashi even l'Chatchilah to be Yotzei through hearing. This is better than not blessing at all.

Kaf ha'Chayim (1): If the latter could bless in another language, but not in Lashon ha'Kodesh, but he understands Lashon ha'Kodesh, they may not divide. He must be Yotzei through listening.

Shulchan Aruch (ibid.): If he does not understand, he is not Yotzei.

Magen Avraham (2): Darchei Moshe and the Bach say that it is good for women to bless for themselves, but the custom is that they listen, like Rashi, and no one protests. This is even for Kidush, which is mid'Oraisa. It is good that they say the Berachah word for word with the Mekadesh or Mevarech. It is impossible to properly have intent and hear.

Mishnah Berurah (5): In other languages, all agree that one is not Yotzei if he does not understand. If one says the Berachah word for word with the Mevarech, all agree that he is Yotzei, even if he does not understand.

Kaf ha'Chayim (2): If women can bless for themselves, this is better even if they understand Lashon ha'Kodesh, and surely if they do not.

Kaf ha'Chayim (4): Even though the Rosh and R. Yonah connote that even one who says the Berachah in Lashon ha'Kodesh must understand it, this is only l'Chatchilah. B'Di'eved he is Yotzei even if he did not understand, unlike one who listens. In other languages, even one who says it must understand to be Yotzei.

Bi'ur Halachah (DH Eino): The Mechaber discusses two. When there are three, Birkas Avraham holds that the Mechaber agrees that one is Motzi others even if they do not understand. Many Poskim bring this. The Bach and Levush connote unlike this.

Kaf ha'Chayim (5): The Beis Yosef (124) holds that even with three, one is not Motzi others who do not understand.

Magen Avraham (2): Some say that even for the seven species we make a Zimun. Therefore, it is good not to fix together on the seven species.

Mishnah Berurah (6): The Birkei Yosef says that the custom is to fix together on the seven species.