Yerushalmi Avodah Zarah 4:9 ירושלמי עבודה זרה ד׳:ט׳

MISHNAH: One may stamp with a Non-Jew in the wine press¹³⁰The grapes are pressed not by a mechanical device but by people stamping on a wooden plank on top of the grapes. All the wine produced is libation wine forbidden for all usufruct. Therefore one could think that a Jew would be forbidden to receive wages for pressing the grapes. But it was explained in the preceding Halakhah that the grape juice turns into wine only by flowing into the cistern below the press. Therefore the Jew may receive wages for pressing the grapes whose juice will not be forbidden at the moment of pressing. but one may not harvest with him¹³¹This Tanna is of the opinion that it is forbidden to cause impurity to fruits of the Holy Land. Since the grapes become impure by being handled by the Non-Jew, a Jewish agricultural worker observing the rules of purity may not help in the Non-Jew’s harvest (cf. Berakhot1:1, Note 3 and Introduction to Tractate Demay p. 349–350).. With a Jew who works in impurity¹³²Working at a time when it was still possible to follow the rules of impurity, a Jew making his wine in impurity was a sinner since he caused his heave and tithes (which are biblical obligations for grain, olive oil, and grape wine) to be impure and therefore forbidden to be consumed by the Cohen. Grapes harvested for wine making are placed in a vat for transport to the wine press. The fluid oozing out of injured grape berries are collected in the vat and also used for making wine. This fluid is welcome; therefore it prepares the grapes for impurity as explained in Demay2:3 Notes 136,137, 141. An observant Jew harvesting together with an unobservant one is guilty of helping to cause impurity to fruits of the Land. There really is no intrinsic reason to forbid pressing the grapes which already are impure; the prohibition to help in pressing is a general rule “not to support sinners”. one neither stamps nor harvests with him but one transports with him amphoras to the wine press and brings with him from the wine press¹³³Transporting empty amphoras to the wine press is not connected with any impropriety; it is not even forbidden to fill impure wine into pure amphoras which thereby will become impure. Transporting amphoras filled with impure wine from the wine press is permitted since all forbidden action was in the past..

HALAKHAH: “One may stamp with a Non-Jew in the wine press,” etc. Rebbi Jonah said, that is, you say only if they walked over it crosswise¹³⁴Since Gentiles are considered impure under the rules of a sufferer from gonorrhea (Babli 36b), the moment a Gentile steps on the planks on top of the grapes everything is impure by “stepping on” (Chapter 3:8, Note 181). It is not really necessary that the Gentile walk on the plank in two different directions. Since then the entire contents of the wine press are impure: the Jew does not help to make them impure.. But if they did not walk over it crosswise, it does not apply. Rebbi Yose asked, if they walked over it crosswise, even following the earlier teaching¹³⁵There seems to be no reason for R. Jonah’s rule since the entire harvest becomes impure at harvest time, Note 132. There never should be any reason not to press grapes with a Gentile.? As it was stated:¹³⁶Tosephta 7:1, Babli 55b. “Originally they were saying that one harvests grapes with the Non-Jew and stamps with a Jew who works in impurity¹³⁷In both sources, one reads: “Originally they were saying that one does not harvest grapes with the Non-Jew and does not stamp with a Jew who works in impurity.” This text must be supposed also for the quote here. If one holds that it is forbidden to cause impurity to the fruits of the Land then one may not harvest with the Gentile because this is the moment when the grapes become impure.. They changed and said, one does not harvest grapes with the Non-Jew nor stamp with a Jew who works in impurity, but one stamps with a Gentile and helps him as long as it did not disappear from sight. Once it disappeared from sight it became libation wine¹³⁸The second part of this baraita parallels the Mishnah; it is missing in the Tosephta. In the Babli text it reads “one does not stamp with the Non-Jew”; this is explained as a precaution because if the Gentile has a small harvest and decided to make red wine by leaving the skins in the fluid, the easiest way would be to plug the pipe leading to the cistern and use the press itself to let the wine ferment. Then the act of pressing makes libation wine and the Jew’s wages would be forbidden for usufruct. The Yerushalmi very reasonably does not consider this a possibility.”.

What is Rebbi Jonah’s reason? Because it already became impure when it was prepared by the grape harvest¹³⁹As explained before, this is R. Yose’s argument.. What is the reason of Rebbi Yose? They were pure by biblical standards. You are the one who decided that they be impure¹⁴⁰This is R. Jonah’s argument. There is no biblical impurity for Gentiles; the laws of impurity are uniquely formulated for Jews. The imputation of impurity (permanent and irrevocable) for Gentiles is rabbinical (Babli 36b). The exclusion of Gentiles from the Temple precinct is not because of impurity but because of their being disqualified.. The strength of Rebbi Yose is the following, as Rebbi Yose said in the name of Rebbi Hila¹⁴¹The source of this statement (in another context) is Ḥallah3:2, Note 53. It should be logical that one may (free)¹⁴²This text makes no sense either by itself nor in this context. Ṭevel is produce under the obligation of heave from which heave was not yet taken; it may not be consumed. By all standards a person is not only permitted but obligated to free his ṭevel by separating the heave. The text in Ḥallah correctly reads: “a person may make his ṭevel impure by biblical standards.” The main point of the argument is given there but omitted here. Heave not only must be consumed in purity but it is stated in Num. 18:8 that the priests have a special duty to guard heave from impurity. It follows that this duty does not apply to ṭevel, which therefore may be allowed to become impure; disagreeing with the hypothesis underlying the Mishnah.
The quote here refers to a different subject. Heave given to Aaron in his quality of priest is pure heave for which he can exercise his duty to watch it and consume it in purity. But once produce has incurred even a doubt of impurity it can no longer be consumed by the Cohen; this eliminates not only the duty of guarding it but all rules made to safeguard it. If the rules of purity no longer can be observed there remain no restrictions on harvesting and pressing grapes with a Gentile. his ṭevel as it is written, you should give from it the Eternal’s heave to Aaron the priest¹⁴³Num. 18:27.. You have to give it to Aaron in his quality of priest. But here, since you cannot give it to Aaron the priest in his quality of priest, you may make it impure.