What is the Difference Between Yayin Nesech and Stam Yainum

What are yayin nesech and stam yainum and what is the difference between them?

Yayin nesech (lit., “poured wine”) refers to wine which was poured in the service of idolatry. The Torah prohibits drinking or deriving any benefit (isur hana’ah) from such wine (Avoda Zara 29b).

Stam yainum refers to wine which might have been poured for an idolatrous service, but we did not see it happen. In the days of the Mishnah, there was a pagan ritual to pour off some wine from every bottle in honor of an idol. Because of the uncertainty, the rabbis decreed that wine that was produced by a nachri, or even kosher wine which was left unattended with a nachri, is forbidden for drinking and benefit because it may have been poured for idolatry. After the rabbinic decree was enacted we treat stam yainum as if we saw it being poured (Tur Y.D. 123).

Even if the nachri who touched the wine was a monotheist, and he would therefore certainly not serve an idol, the rabbis still forbade the wine, for another reason—because sharing wine can lead to intermarriage. However, in this case, it is only forbidden to drink the wine, but one may benefit from this wine in other ways (e.g., it may be bought and sold). (See Shulchan Aruch Y.D. 123:26 and Shach 123:51.)

Once it is cooked (mevushal), kosher wine does not become forbidden even if touched by a nachri (Shulchan Aruch Y.D. 123:3).

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