The Gemara asks: If so, if this is indeed Rabbi Shimon’s opinion, why, then, does he specifically state that meat cooked in milk is susceptible to impurity because it had a period of susceptibility to contracting impurity before they were cooked together? Derive this halakha from the fact that it is food that you can feed to others, as Rabbi Shimon maintains that deriving benefit from meat and milk cooked together is not prohibited.

As it is taught in a baraita: Rabbi Shimon ben Yehuda says in the name of Rabbi Shimon: With regard to meat cooked in milk, eating it is forbidden and deriving benefit from it is permitted, as it is stated: “For you are a holy people to the Lord your God; you shall not cook a kid in its mother’s milk” (Deuteronomy 14:21). And elsewhere the verse states: “And you shall be holy men to Me; therefore you shall not eat any flesh that is torn by animals in the field” (Exodus 22:30). Just as there, with regard to an animal torn by animals, which is forbidden as a tereifa, i.e., an animal possessing a wound that will cause it to die within twelve months, eating it is forbidden but deriving benefit from it is permitted, so too here, with regard to meat cooked in milk, where the verse mentions being holy just as the other verse did, eating it is forbidden but deriving benefit from it is permitted.

The Gemara answers: The baraita that cites Rabbi Shimon’s opinion states one reason why meat cooked in milk is susceptible to impurity and adds another. One reason is because it is food that you can feed to others. Therefore, it is called food for the purpose of being susceptible to impurity. And another reason is because even for him, i.e., a Jew, although eating the milk and meat is currently prohibited, it had a time when it was fit for consumption, i.e., before they were cooked together, and therefore they remain susceptible to impurity.

The opinion of Rabbi Shimon that all items from which deriving benefit is prohibited are not susceptible to the impurity of food except for meat cooked in milk has been elucidated. Rava now proceeds to explain his proof that even according to Rabbi Shimon, deriving benefit from a firstborn donkey after the breaking of its neck is forbidden: And if it is so, that after breaking the neck of the firstborn donkey Rabbi Shimon deems it permitted for one to derive benefit from it, let the tanna teach: And Rabbi Shimon concedes with regard to a firstborn donkey and meat cooked in milk, that they are susceptible to the impurity of food. Since a firstborn donkey is not listed as an exception, Rabbi Shimon must hold that it is prohibited to derive benefit from it after its neck is broken, and it is therefore not susceptible to impurity.

The Gemara responds: If it is a case where the one who broke the neck of the donkey intended at the time that people would eat from it, so too it would be susceptible to the impurity of food according to Rabbi Shimon, as it is permitted to derive benefit from it. Here we are dealing with a case where he did not intend for it to be eaten, as even gentiles do not usually consume the meat of a donkey, and it therefore is not considered food.

The Gemara asks: But if he did not intend for anyone to eat it, what is the reason the Rabbis deem the flesh susceptible to the impurity of food? The Sages said before Rav Sheshet: It is susceptible to the impurity of food because the prohibition to eat it serves as intent to treat it as food, i.e., the very fact that it is forbidden renders it significant enough to be deemed a food.

The Gemara asks: But according to the Rabbis, did they actually say that an item is susceptible to the impurity of food since its prohibition serves as its intent? But didn’t we learn in a mishna (Teharot 1:1) that the Sages stated thirteen matters concerning the unslaughtered carcass of a kosher bird, and this is one of them: It requires explicit intent that it will be eaten in order to become susceptible to the impurity of food, as most gentiles are unaccustomed to eating it, but it does not require contact with liquid to be rendered susceptible to ritual impurity.

And if the logic of: Its prohibition serves as its intent, is accepted, why do I need the intent here, as an unslaughtered carcass is forbidden to be eaten? The Gemara answers: In accordance with whose opinion is this? It is in accordance with the opinion of Rabbi Shimon, who does not hold that its prohibition serves as its intent.

The Gemara suggests: Come and hear a proof from another mishna (Okatzin 3:3): A carcass of a non-kosher animal, such as a horse or donkey, found in any location; or an unslaughtered carcass of a kosher bird or the fat of a kosher animal found in the villages, where the local gentiles are unaccustomed to eating it, all require intent to consume it in order to become susceptible to the impurity of food, but they do not require being rendered susceptible to impurity by coming in contact with liquid. And if you say its prohibition serves as its intent, why do I need intent? All these foods are forbidden for consumption by a Jew. The Gemara responds: In accordance with whose opinion is this? It is in accordance with the opinion of Rabbi Shimon.

The Gemara suggests: Come and hear a proof from the continuation of the same mishna: An unslaughtered carcass of a kosher animal found in any location, or the unslaughtered carcass of a kosher bird found in any location, or the fat of a kosher animal found in the marketplaces, i.e., in a large city that has marketplaces, where some people do eat it, do not require intent for consumption in order to be regarded as subject to impurity, as they are presumed to be food for gentiles; nor do they require contact with liquid in order for them to be rendered susceptible to impurity. The Gemara infers that only the carcass of a kosher animal does not require intent, but the carcass of a non-kosher animal requires intent. If its prohibition serves as its intent, why does it require intent for consumption?

And if you would say: In accordance with whose opinion is this, it is also in accordance with the opinion of Rabbi Shimon; one could respond that since the latter clause is the opinion of Rabbi Shimon it follows that the former clause, which is written without attribution, is not in accordance with the opinion of Rabbi Shimon. As the latter clause teaches: Rabbi Shimon says even the meat of the camel, and the hare, and the rock badger, and the pig do not require intent or contact with liquid to be rendered susceptible to impurity. And Rabbi Shimon said: What is the reason? The reason is that they have some characteristics of kosher animals (see Leviticus 11:4–7). If so, the dispute between Rabbi Shimon and the Rabbis cannot be based on whether the prohibition of the animal serves as its intent.

Rather, Rava says: Everyone, including the Rabbis, agrees that we do not say its prohibition serves as its intent. And with regard to a firstborn donkey, if one broke its neck, so too, the Rabbis hold that it is not susceptible to the impurity of food, since the one who broke its neck did not intend for it to be eaten.