This link between cooking and eating indicates that since one is not flogged for eating forbidden fat cooked in milk, as agreed upon above, one also is not flogged for cooking the two together.

And some say the opposite: With regard to cooking, everyone agrees that one is flogged for this act, since the principle of a prohibition not taking effect where another prohibition already exists is not relevant. When they disagree, it is with regard to eating. The one who says he is not flogged applies the principle that a prohibition does not take effect where another prohibition already exists, and the fat was already prohibited for consumption in its own right before being cooked with milk. And the one who says he is flogged holds that it was for this reason that the Merciful One expressed the prohibition of eating meat cooked in milk using the language of cooking, to teach that since one is flogged for cooking forbidden fat in milk, one also is flogged for eating the product.

The Gemara suggests a third explanation of the dispute between Rabbi Ami and Rabbi Asi: And if you wish, say that one Sage said one statement and one Sage said another statement, and they do not disagree, as they are referring to different cases. The Sage who said that one is flogged is referring to the transgression of cooking forbidden fat with milk, whereas the one who said one is not flogged is referring to the consumption of forbidden fat with milk. Everyone agrees that a prohibition does not take effect where another prohibition already exists, and therefore one is flogged only for cooking forbidden fat in milk, but not for eating the two together.

The Gemara raises an objection from a Tosefta (8:3): One who cooks meat in whey, the liquid leftover after milk has been curdled, is exempt from lashes, as whey is not defined as milk for purposes of the prohibition. Likewise, for blood that one cooked in milk, he is exempt, as blood is not considered meat. Similarly, with regard to the bones, the tendons, the horns, and the hooves that one cooked in milk, he is exempt.

The Tosefta continues: By contrast, with regard to prohibited piggul meat, i.e., meat from an offering that was sacrificed with the intent to sprinkle its blood or partake of its meat beyond its designated time, and similarly prohibited notar, meat from an offering whose period for consumption has expired, and the prohibited impure meat of an offering, that one cooked in milk, he is liable to be flogged for violating the prohibition of meat cooked in milk. This indicates that the prohibition applies to items already prohibited for consumption, contrary to the above opinion attributed to Rabbi Ami and Rabbi Asi.

The Gemara answers: This tanna of the baraita maintains in general that a prohibition takes effect where another prohibition already exists, whereas Rabbi Ami and Rabbi Asi are of the opposite opinion. It is conceivable that these Sages, who are amora’im, disagree with that tanna, as the issue of whether a prohibition takes effect where another prohibition already exists is a well-known dispute among the tanna’im themselves.

§ It was stated in the above baraita: One who cooks meat in whey is exempt from lashes. The Gemara comments: This ruling supports the opinion of Reish Lakish, as we learned in a mishna, with regard to liquids that render food susceptible to ritual impurity (Makhshirin 6:5): The halakhic status of whey is like that of milk, which is one of the liquids that render food susceptible to impurity, and the halakhic status of olive secretion is like that of oil, which also renders food susceptible to impurity. With regard to this mishna, Reish Lakish says: They taught this halakha only with regard to rendering seeds, i.e., produce, susceptible to impurity. But with regard to cooking meat in milk, the halakhic status of whey is not like that of milk.

§ The Sages taught in a baraita: From the phrase “in its mother’s milk” I have derived only that the prohibition applies to the mother goat’s milk. From where do I derive that it also applies to the milk of a cow and a ewe?

You can say an a fortiori inference: Just as a kid’s mother, which is not prohibited for mating with the kid, as they are of the same species, is nevertheless prohibited for cooking with it, as stated in the verse, is it not right that a cow or a ewe, which are prohibited for mating with it, as they are of different species, should be prohibited for cooking with it? Therefore, the verse states elsewhere: “In its mother’s milk,” a second time, to include a cow and a ewe.

The Gemara challenges the conclusion of the baraita. But why do I need a verse? It was just derived through the a fortiori inference.

Rav Ashi said: It is needed because one can say that the refutation of the a fortiori inference is present from the outset, i.e., there is a difficulty with the comparison: From where do you derive the inference? It is derived from its mother goat, which the baraita presents as being treated more leniently than a cow or ewe since it may be mated with a kid. But there is a stringent aspect of the mother goat not shared by a cow or ewe: What is unique about its mother? It is unique in that it is prohibited for slaughter with it, since one may not slaughter an animal and its mother on the same day (see Leviticus 22:28). Will you say the same about a cow, which is not prohibited for slaughter with it? Therefore, the verse states: “In its mother’s milk,” to include a cow and a ewe.

§ The above baraita accounts for two of the Torah’s three mentions of the phrase “in its mother’s milk.” The Gemara now addresses the third. It is taught in another baraita: From one instance of the phrase “in its mother’s milk” I have derived only that the prohibition applies to the milk of its mother, if the mother is less than a year old and has not yet entered the pen for the purpose of its owner’s separating the annual animal tithe. From where do I derive that it also applies to the milk of its older sister, i.e., one that is more than a year old that has already entered the pen for the animal tithe in the previous year?

You can say an a fortiori inference: Just as a kid’s mother, which enters the pen to be tithed with it, is nevertheless prohibited for cooking with it, is it not right that its sister, which does not enter the pen to be tithed with it, should be prohibited for cooking with it? Therefore, the verse states elsewhere: “In its mother’s milk,” a third time, to include the older sister in the prohibition.

The Gemara asks: But why do I need a verse? It was just derived from the a fortiori inference. Rav Ashi said: It is needed because one can say that the refutation of that a fortiori inference is present from the outset. From where do you derive the inference? It is derived from its mother. But one may respond: What is unique about its mother? It is unique in that it is prohibited for slaughter with it on the same day. Will you say the same halakhot apply to its older sister, which is not prohibited for slaughter with it? Therefore, the verse states: “In its mother’s milk,” including the older sister.

The Gemara continues: We have found a source for the halakha that its older sister is included in the prohibition of meat cooked in milk. From where is it derived that the same applies to its younger sister, one that has not yet entered the pen for the tithe? The Gemara responds: It is derived from between them, i.e., from the combination of the mother and the older sister.

The Gemara elaborates on the need for both cases in order to derive the third: From which of the two cases should it be derived? If it should be derived from its mother, one can claim: What is unique about its mother? It is unique in that it is prohibited for slaughter with it on the same day, unlike the younger sister. One may respond: Its older sister can prove the point, since it is not prohibited for slaughter with the kid, but it is still included in the prohibition of meat cooked in milk. But this can be refuted as well: What is unique about its older sister? It is unique in that it does not enter the pen to be tithed with it, unlike the younger sister. One may respond that its mother can then prove the point, as it can enter the pen to be tithed with the kid and is still included in the prohibition.

And consequently, the inference has reverted to its starting point: The aspect of this case is not like the aspect of that case and the aspect of that case is not like the aspect of this case; their common element is that both the mother and older sister are meat and it is prohibited to cook them in milk. If so, I will also include its younger sister in the prohibition, since it is also meat, and therefore it is prohibited to cook it in milk.

The Gemara challenges: If so, the inclusion of its older sister in the prohibition can also be derived from between them, i.e., from the combination of the kid’s mother and a cow. Although both a cow and the mother possess unique stringencies not shared by the older sister, i.e., the prohibition of mating and of slaughtering with the kid, respectively, neither possesses both stringencies, and the halakha with regard to the older sister can be derived from their common element, i.e., that they are both meat and prohibited to cook in milk, as stated above. If so, what need is there to derive this halakha from the verse?

The Gemara responds: Yes, it is indeed so; the halakha with regard to the older sister is derived from the common denominator of the mother and a cow. Rather, why do I need the verse’s additional mention of the phrase “in its mother’s milk?” It is necessary for that which is taught in a baraita: When the verse states: “In its mother’s milk,” I have derived only the prohibition to cook the kid in its mother’s milk;