Chukát / cháláv sztám

Rabbi Judah said: Rabbi Ishmael put this question to Rabbi Joshua as they were walking on the way, “Why have they forbidden the cheese of non-Jews?” He replied, because they curdle it with the rennet of a nevelah (an animal that was not properly slaughtered.” He (Rabbi Ishmael) said: “but is not the rennet of a burnt-offering more strictly forbidden than the rennet of a nevelah? [and yet] it was said that a priest who is not fastidious may suck it out raw.” (Though the Sages disagreed with this opinion, and they said that no benefit may be derived from it, although one who consumed it did not trespass [temple property). Rabbi Joshua responded: “The reason then is because they curdle it with the rennet from calves sacrificed to idols.” He (Rabbi Ishmael) said to him: “if that be so, why do they not extend the prohibition to any benefit derived from it?” He (Rabbi Joshua) diverted him to another matter, saying: “Ishmael, how do you read for your [masc.] love is more delightful than wine” or “your [fem.] love etc. (Song of Songs 1:2” He replied: “your [fem.] love is better …” He said to him: this is not so, as it is proved by its fellow [-verse]: your ointments [masc.] have a goodly fragrance … [therefore do the maidens love you] (Song of Songs 1:3).”

The following articles of non-Jews are prohibited but the prohibition does not extend to deriving benefit from them: 1. milk which a non-Jew milked without an israelite watching him, 2. their bread and oil (Rabbi and his court permitted the oil) 3. stewed and pickled things into which they are accustomed to put wine or vinegar, 4. pickled herring which had been minced, 5. brine in which there is no kalbith-fish floating, 6. helek, 7. pieces of asa foetida 8. and sal-conditum. Behold these are prohibited but the prohibition does not extend to deriving benefit from them.

MISHNA: This mishna lists items belonging to gentiles which it is prohibited to consume, but from which it is permitted to derive benefit. And these are items that belong to gentiles and are prohibited, but their prohibition is not that of an item from which deriving benefit is prohibited: Milk that was milked by a gentile and a Jew did not see him performing this action, and their bread and oil. The mishna notes that Rabbi Yehuda HaNasi and his court permitted the oil of gentiles entirely.

Accordingly, logic would dictate that any milk found in the possession of a gentile is forbidden, lest the gentile have mixed the milk of a non-kosher animal with it. And the cheese of the gentiles should be permitted, for the milk of a non-kosher animal will not form cheese. Nevertheless, during the age of the Sages of the Mishnah, they issued a decree against gentile cheese and forbade it, lest they use the skin of the stomach of an animal they slaughtered - which is forbidden as a nevelah - to cause it to solidify.
If one would say: The stomach skin is a very small entity when compared to the milk that it is used to solidify. Why is it not nullified because of its insignificant size? Because it is used as the catalyst to cause the cheese to curdle. Since the catalyst which causes it to curdle is forbidden, everything is forbidden, as will be explained.

Milk that was milked by non-Jews and no Jew saw them do so, it is forbidden as perhaps non-kosher milk was mixed in. If it was milked in his house and a Jew was sitting outside, if it is known that there is no non-kosher animal in his herd, it is permitted, even if no Jew is able to see him at the time that he milks the animal. If he has a non-kosher animal in his heard, and the Jew sits outside, and the non-Jew is milking only for the sake of the Jew, even if the Jew is unable to see him when he is sitting, if he is able to see him when he stands, this is permitted, because the non-Jew fears that perhaps he will stand and be seen, and he knows that non-kosher milk is forbidden to the Jew. Rema: Initially, it is necessary for the Jew to be there are the beginning of the milking and check to make sure that the bucket is empty and does not contain non-kosher milk. And it is our custom to be stringent and not milk with vessels which are usually used for milking by non-Jews, lest some of their [non-Kosher] milk remain in the vessel. In any case, after the fact there is no need to be concerned for this. And regarding maidservants that milk domestic animals in the Jew's house or in his [animal] pen, any instance in which it is not a house of a non-Jew, that is enough and there is no need to be concerned about a non-kosher matter, and it is permitted even initially to leave them to milk even there is not a Jew around, because the non-Jewish milker is in his house or neighborhood, they are not suspected of milking non-kosher animals. But if a non-Jew takes a break, the Jew needs to be there, because it is like the case of the non-Jew's house. And even a Jewish child will suffice, because the non-Jew fears in their presence. In any case, if a Jew is not present until after he has finished milking, this milk is considered the milk of non-Jews that is forbidden, even thought no non-kosher animal exists in his herd. Milk of a non-Jew makes vessels non-kosher when they are cooked in them, just as any prohibited food, even though this is only an uncertainty whether he has mixed in something non-kosher. And so too with non-Jewish cheese, but not non-Jewish butter, even in a place where it is considered prohibited it does not prohibit vessels when cooked, and it is not a problem if it becomes mixed; if it is mixed in that which is permitted, everything is permitted, like above regarding the bread of non-Jews. See above in chapter 112. Milk of non-Jews that is forbidden, it will not work to make it into cheese or butter afterwards, rather it remains forbidden, and everything that is made from it is forbidden.