פירוש על עבודה זרה 58:3

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.