Avodah Zarah 4:8-9

Avodah Zara 4:8

One may buy a winepress full of already-tread grapes from a non-Jew even though the latter takes the grapes and puts them on the heap (from where the juice flows into the vat); the grape juice doesn’t become libation wine until it runs into the vat. What has already run into the vat is prohibited but the rest is permitted.

Avodah Zara 4:9

A Jew may tread grapes in the winepress together with a non-Jew but he may not harvest grapes together with him. If a Jew treads grapes in a state of ritual uncleanliness (which is prohibited), one may neither tread nor harvest grapes with him (because that would be assisting him in transgression) but one may bring barrels to and from the winepress with him. If a baker works in a state of ritual uncleanliness (which is prohibited), one may neither knead nor roll dough with him but one may take bread to the bakery with him.