Commentary for Avodah Zarah 63:17

Beer vinegar may be prohibited because it may contain wine yeast (the dregs would be used to re-ferment the beer). But if taken from a storehouse, we can assume it has no wine in it.

The first attempt to understand this term seems to be that it is simply related to the emperor Hadrian. Rashi explains that his troops took it with them when they went on long journeys to battle. It is unclear whether this is connected with what appears below.

R. Dimi explains that Hadrianic earthenware was an ancient way of making instant wine. Sort of like a tea bag for wine.

Roman instant wine was even better than Jewish first quality wine. I guess they were drinking Manischewitz back then as well.

The Jew does not want to use the earthenware for the wine that is in it. He wants to use the shard only to even out the legs of the bed. In an abstract formulation, this is called “one who wants the object (the shard) to exist for some reason other than the prohibited substance (the wine). Two amoraim argue over whether such a usage transgresses the prohibition of using Hadrianic earthenware.

The end of this baraita is a difficulty on the amora who said that as long as the Jew uses the object for some other purpose, besides benefiting from the wine in it, the act is permitted. In this case, the Jew wanted to use it only to cover his donkey. He did not care about the wine, and nevertheless it is prohibited.

The Talmud responds by taking note of a contradiction between the two halves of the baraita. The first half allows one to sell earthenware flasks belonging to non-Jews even though there is wine absorbed in the flask. Assumedly this is permitted because the Jew is benefiting from the flask and not the wine absorbed in it. The second half prohibits using the leather flask for any use whatsoever, even if the Jew does not care about the wine and wishes to use only the leather.

Rava explains that in the second half of the baraita the issue is not directly deriving benefit from the leather flask with non-Jewish wine in it. If this were the only issue, the act would be permitted. The problem is that he might use this leather to close his own flask. Should he do so, he might come to mix his own wine with the non-Jewish wine, and this is prohibited. In contrast, there does not seem to be such fear when it comes to using Hadrianic earthenware to support the bed.

The Talmud now asks why one would allow the sale of earthenware flasks but not supporting a bed with the Hadrianic earthenware. The answer is that when it comes to the latter, they are so thoroughly saturated with wine that the prohibited substance is “there.” In contrast, the wine soaked into regular earthenware flasks is not really “there.” It is present in only trace amounts.

There are two solutions to the contradiction between these two baraitot. According to the first solution, the earlier baraita meant that the other sages disagree with Rabban Gamaliel, but Rabban Gamaliel’s own son did agree with him, and that is what is meant by the above baraita.
The other solution is that there are two different rabbis who transmit this incident—each with almost the same name, but different. The first is Shimon ben Gudda with an aleph at the end and the second is Shimon ben Gudda’ with an ayin at the end. I’ll admit that this is a strained solution, but nevertheless, Jews probably did pronounce the ayin and the aleph different.

The mishnah taught that it is prohibited to derive benefit from skins pierced at the heart. It is assumed that such skins were part of idolatrous practice. This section defines precisely what this heart-pierced skin is.
The presence of the blood is necessary to determine whether the hole was made while the animal was alive. If the hole was made after its death, then there should be no blood and it is permitted. Unless the skin was salted in which case we can assume that the salt removed the blood.