Talmud - Nedarim 54b נדרים נ״ד ב׳

doesn’t Rabbi Akiva concede that the agent must consult his employer? Because he failed to do so and acted on his own, he is not considered to have performed his mission. This halakha was stated before Rava. He said to those who stated the halakha before him: Naḥmani, i.e., Abaye, spoke well.

§ The Gemara asks: Who is the tanna who disagrees with the opinion of Rabbi Akiva in the mishna here? The Gemara answers: It is Rabban Shimon ben Gamliel, as it is taught in a dispute in the baraita: For one who vows that meat is forbidden to him, it is prohibited to eat all types of meat, and it is prohibited for him to eat meat of the head, and of the feet, and of the windpipe, and of the liver, and of the heart, although people do not typically eat meat from those parts of the body. And it is prohibited for him to eat meat of birds, as it too is popularly called meat. However, it is permitted for him to eat of the meat of fish and grasshoppers, as their flesh is not called meat.

Rabban Shimon ben Gamliel says: One who vows that meat is forbidden to him, is forbidden in all types of meat, and is permitted to eat meat of the head, and of the feet, and of the windpipe, and of the liver, and of the heart and of birds, and needless to say he may also partake of fish and grasshoppers. And Rabban Shimon ben Gamliel would likewise say: Innards are not considered meat, and one who eats them is not a person, meaning that the innards are not fit for human consumption. The Gemara elaborates: With regard to one who eats them, in terms of the halakhot related to their consumption, e.g., vows, they are considered as meat. However, with regard to purchase, one who purchases them is not a person. In any case, apparently, Rabban Shimon ben Gamliel disagrees with Rabbi Akiva, as he maintains that although if an agent fails to find meat he is required to consult his employer before replacing it with liver, it is not considered meat with regard to vows.

The Gemara asks: What is different about the meat of a bird according to the first tanna, that he prohibits it since it is considered meat, due to the fact that when the agent fails to find meat, he tends to consult his employer about it? The same should be true of the meat of fish too. If the agent does not find meat, he tends to consult his employer about it, as he says: If I do not find meat, should I bring fish? And therefore, let fish also be forbidden according to the first tanna.

Abaye said: This is referring to a case where he let his blood when he vowed, as a person in that condition does not eat fish. It was common knowledge then that eating fish after bloodletting is harmful. The Gemara asks: If so, he would not eat birds either, as Shmuel said: With regard to one who lets blood and eats the meat of a bird, his heart rate accelerates and flies like a bird. Clearly, bird meat too is deleterious for his health. And it is taught in a baraita: One neither lets blood before eating fish, nor before eating birds, nor before eating salted meat. And it is taught in another baraita: If one let blood, he may eat neither milk, nor cheese, nor eggs, nor cress, nor birds, nor salted meat. The Gemara answers: Meat of birds is different, as it is possible to eat it safely after bloodletting by means of thoroughly boiling it.

Abaye said: This is referring to a case where his eyes hurt him, as fish are harmful for eyes. Therefore, meat of birds is permitted, but not fish. The Gemara asks: If so, and he is suffering from eye pain, he should eat fish, as Shmuel said an acronym: Nun, samekh, ayin, which stands for: Nuna samma la’einayim, which means: Fish is a medicine for eyes. The Gemara answers: That statement of Shmuel is referring to the latter stages of the eye infection.

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Nedarim 54b explores rabbinic debate over which meat cuts a vow prohibits, plus a dispute on an agent's duty to consult his employer.