Beraisa (R. Hoshiya): A person should answer "Amen" even if he did not eat, but he should not answer "Blessed by the One from Whom we ate" unless he actually ate.

Beraisa: One may not answer an "orphaned Amen", nor a "cut Amen".

What is an "orphaned Amen"? R. Huna said - If a person wishes to fulfill his obligation to recite a certain Berachah by answering Amen to someone else's Berachah, but he did not hear the Berachah; even if he knows which Berachah was said, he should not answer Amen - if he does, it is called an "orphaned Amen". If he does not have an obligation to recite the Berachah, he may answer Amen even if he did not hear it, as long as knows which Berachah is being recited. (Note: According to the Pnei Moshe, this entry simply refers to answering Amen without knowing which Berachah was made.)

Beraisa: If an idolater blessed Hash-m with a blessing of praise, one may answer Amen; if he recites a blessing of thanks, one may not answer Amen. (Note: See Shayarei Korban, found at the back of the Gemara).

R. Tanchuma: If an idolater blesses you, you should answer Amen, as the Pasuk states (Devarim 7, 14), "You shall be blessed from all of the nations".

An idolater once met R. Yishmael and blessed him.

R. Yishmael responded - Your words are already stated in the Torah (and there is no need to respond in kind).

Another idolater met him a cursed him.

R. Yishmael responded - Your words are already stated in the Torah.

His students said to him - How could you answer the second one as you answered the first?

R. Yishmael responded - Does the Pasuk not say (Bereishis 27, 29), "Those that curse you will be cursed and those that bless you will be blessed".

Rebbi would repeat the P'sukim from "Ana Hash-m" onwards. R. Elazar ben Parta did not repeat.

R. Elazar: (The Mishnah had taught that if one buys a Lulav from an ignoramus during the Shemita year, he should be given the Esrog as a gift but he may not buy it.) This the opinion of the Elders of the Galil who say that it is prohibited to give two meals-worth of Shemita money to one who is suspected of transgressing the laws of Shemita. (Therefore, under no circumstances may one buy a Shemita Esrog from an ignoramus, since it is always worth at least three meals.)

R. Matanya: The Mishnah could fit into both opinions - if the Esrogim are highly priced (even the Rabbanan would agree that one may not buy the Esrog).

(He should give the Esrog as a gift) It is like the story in Terungaya where Rav Nachman bar Yaakov gave an Esrog to his son as a gift and told him, "When you have acquired it and used it for the Mitzvah, return it to me".