Commentary for Avodah Zarah 58:9

A Jew may not benefit from the wine of non-Jews since it may have been used in making a libation to an idol. [This prohibition is still observed by many religious Jews today, even though we can be quite sure that the wine was not used for idol worship. We will learn a lot more material about non-Jewish wine at the end of this tractate.] Similarly, vinegar that was once intended to be wine and then went sour may not be used by a Jew, since it may have been used in idol worship when it was wine. However, if the non-Jew bought the vinegar from a Jew and then gave it back to a Jew the Jew may use it since vinegar itself is not used in idol worship.
According to the Talmud Hadrianic earthenware absorbs wine and when subsequently wetted, will release the wine. If a Jew were to use such earthenware he would be using non-Jewish wine, which is prohibited.
According to the mishnah, idolaters would make incisions in animals to remove animal hearts and use them in idol worship. If one sees a cut in an animal skin at the place of the heart, it is a sign that the animal was used for idol worship and it is forbidden. Rabban Shimon ben Gamaliel claims that only if the cut is circular is the skin forbidden. Since non-Jews do not make oblong cuts as part of their idol worship, the skin is permitted.

Meat that is being brought into a place of idol worship is permitted to a Jew, since it has not yet been used for idol worship. It is of course not permitted to be eaten, since it probably is not kosher. However, one could use it to feed animals. Meat that is coming out of a place of idol worship is forbidden, since it was probably used for idolatry.

It is forbidden to conduct business with non-Jews who are on their way to worship idols, since they will thank their gods for their business with the Jews. In this way the Jew will indirectly be abetting idol worship. However, it is permitted to engage them in business on their return, since they have already completed their idol worship. [Note this last section is of a different subject than the other sections. It should have been included in chapter one. It probably was included here due to its similarity to the previous clause.]

If a Jew stores his wine in skin-bottles or ceramic flasks in which non-Jews previously stored their wine the Jewish wine becomes forbidden. Since the skin-bottles and flasks contained absorbed wine in their walls, that non-Jewish wine would mix with the Jewish wine. According to Rabbi Meir, it is forbidden to even derive any benefit from this wine. According to the Sages it is only forbidden for the Jew to drink the wine. If he wants he could sell the wine to a non-Jew and thereby derive benefit. The Sages rule that the only type of non-Jewish wine from which it is actually prohibited to derive benefit is wine that one can see. Wine that has been absorbed in a vessel is only forbidden to be drunk.

According to Rabbi Meir, both dry and moist grape skins and seeds that belonged to non-Jews are forbidden to Jews and the prohibition extends even to deriving any benefit from them. The Sages rule that dry seeds and skins are permitted even to eat and only moist ones are prohibited.

The concern with regards to fish brine is that there may be small amounts of wine in it. Bithynian cheese is cheese that comes from a place called Bithynia, which is in Asia Minor. According to the Talmud most of the calves raised there were used for idol worship. Since cheese uses rennet, a substance which comes from the stomach lining of a cow and solidifies the milk into cheese, we are concerned that the rennet came from a cow used in idol worship. Due to our concern with both of these foods, Rabbi Meir says it is forbidden for a Jew to derive benefit from either. According the Sages it is only forbidden to eat them; it is permitted to derive benefit from them. The fish brine is permitted since the wine was only used as an antidote for any polluting agent in the brine and not for its own taste. The cheese is permitted since most of the animals in Bithynia were not used for idol worship, only most of the calves which were a minority of the total number of animals.

Rabbi Ishmael asks Rabbi Joshua why the Sages forbid cheese made by non-Jews. This prohibition is perplexing to Rabbi Ishmael because even the non-Jews make their cheese from kosher animals such as cows and goats. Since the milk used to make the cheese comes from kosher animals, it should be permitted.
Rabbi Joshua responds that non-Jews use rennet to curdle the cheese. This rennet comes from the stomachs of animals that were not properly slaughtered and therefore the cheese is prohibited.

Rabbi Ishmael responds that a priest who sees rennet in the stomach of a whole burnt offering may drink this rennet (I know this sounds a little gross.). Since a whole burnt offering is forbidden to be eaten, this law proves that the rennet is not considered part of the animal. If it were considered to be an integral part of the animal, it would have been prohibited. Since it is not forbidden in this case then by comparison the rennet used to make cheese should not make the cheese forbidden to Jews, even though it comes from an animal that was improperly slaughtered.
At this point the mishnah offers an aside. The statement that the rennet of a whole burnt offering may be consumed by a priest was only Rabbi Ishmael’s opinion. The Rabbis did not agree with him. They stated that it is forbidden to derive benefit from this rennet and yet one who does so is not considered to have taken (trespassed) Temple property. [If he had taken from Temple property he would have to bring a sacrifice to atone for the sin, as well as pay back the value of that which he took.] This section is not an integral part of the mishnah and was added in at a later time.

Rabbi Joshua now provides another reason why non-Jewish cheese is forbidden. Non-Jews use rennet that comes from calves that were used in idol worship. Since any item that was used in idol worship is forbidden to a Jew, non-Jewish cheese is forbidden to a Jew.

Rabbi Ishmael responds that if non-Jewish cheese is forbidden since it may contain rennet that comes from an animal used in idol worship, then it should not only be forbidden to eat, it should also be forbidden to derive any benefit from it. From the example in the previous mishnah concerning Bithynian cheese, we learned that the Sages said it was only forbidden for consumption and it was not forbidden to derive benefit from non-Jewish cheese.

Rabbi Joshua does not seem to have an answer to this response of Rabbi Ishmael’s and therefore he distracts him to a different topic, this dealing with the gender of the speaker in the second verse of Song of Songs. The verse states “for your love is more delightful than wine”. “Your love” can either be masculine or feminine. The only difference in the Hebrew is the vocalization; the consonants are exactly the same. Rabbi Ishmael responds that he vocalizes it to be a masculine pronoun. In other words the speaker is feminine and she is speaking to a male. Rabbi Joshua points out that this is surely wrong for the word “your ointments” is masculine. Although this word too can be vocalized to be feminine, the fact that the end of the verse refers to maidens loving him proves that the one being spoken to is male.
Scholars have attempted to connect the meaning of this section with the previous topic of cheese. The “masculine” version of the verse gives priority to the written Torah, which would prohibit cheese only if it uses non-kosher ingredients, such as nevelah. R. Joshua is arguing that if cheese is prohibited, it must be prohibited on these grounds. The feminine version of the verse prioritizes the oral Torah, that created by the rabbis. Thus R. Ishmael believes that non-Jewish cheese is prohibited by rabbinic decree, like wine, as a means to keep Jews and non-Jews apart.

The Talmud learns the prohibition of libated wine from the comparison the verse makes with idolatrous sacrifices.

The Talmud now asks the obvious question—how do we know that idolatrous sacrifices are prohibited. This is derived from Psalms which compares sacrifices to the dead. It is prohibited to derive benefit from body parts of the dead (unless one is doing so to save a life, so organ transplants are allowed).

The chain of deriving laws continues! How do we know that one may not benefit from the dead? Because of a “gezerah shavah” (a comparison of the same word used in two different contexts) connecting it with the heifer whose neck must be broken when a body is found and the murderer is not known. It is forbidden to derive benefit from this heifer.

How do we know that one may not derive benefit from the red heifer? Because it is an act of atonement, like a sacrifice. And just as one may not derive benefit from sacrifices (except for specifically prohibited acts like eating), so too one may not derive benefit from the heifer.

The Talmud finds the mishnah’s prohibition of gentile wine to be obvious—just because the wine goes bad does not mean that it becomes permitted.
Rav Ashi answers that there is one point of leniency with regard to vinegar. Most of the time, if a non-Jew handles Jewish wine, it must be doubly sealed. This is a halakhah we will deal with at greater length later in the tractate. But Jewish vinegar being held by a non-Jew does not need to be doubly sealed. First of all, non-Jews don’t generally libate vinegar (although they might, for the line between wine and vinegar is not so hard). Second, he won’t trouble himself to exchange this wine for his own because it does have at least one seal, making it harder to open.

This is the same passage as above but about cooked wine. Cooked wine does not need two seals (today cooked wine can be handled by a non-Jew because we are more lenient today about wine because non-Jews do not libate. But in the Talmud they were still strict).