The 194th prohibition is that we are forbidden from drinking yayin nesech [wine used for idolatry].

There is no verse that states this prohibition explicitly. However, [the prohibition is derived from a verse by] the Sages in Avodah Zorah,1 "The verse2 says, 'They eat the fat of their sacrifices; they drink the wine of their libations' — just as the sacrifice is prohibited, so too the wine is prohibited."

You are aware that one is prohibited from deriving benefit from it, and the punishment [for drinking it] is lashes, as is well known throughout the Talmud.

The proof that yayin nesech is a Biblical prohibition and that it counts as one of the [365] prohibitions is the statement of the Sages in Gemara Avodah Zorah,3 "Rabbi Yochanan and Reish Lakish both say that all prohibitions of the Torah — regardless whether they were mixed into the same type or a different type — [are prohibited only] when the taste is perceptible; with the exception of tevel and yayin nesech, which, when mixed into the same type are prohibited even in the smallest amount, but when mixed into a different type, are prohibited only when the taste is perceptible."4 This is a clear proof that yayin nesech is one of the prohibitions of the Torah.5

The Sifri6 also, when mentioning the decline of the Jewish people in Shittim in acting immorally with the daughters of Moav,7 says, "He entered [her tent], and she had a bottle full of Ammonite wine with her, and non-Jewish wine had not yet been prohibited to the Jewish people. She said to him, 'Would you like to drink?' etc." This that they said, "and non-Jewish wine had not yet been prohibited to the Jewish people," undoubtedly implies that later on8 it was indeed prohibited.

However, this that the Sages included wine among the 18 Rabbinic decrees;9 and so too their statement,10 "Yayin nesech is different, because the Sages were especially strict in its regard" [implying that the prohibition is only Rabbinic in nature] — they are referring to stam yaynom,11 not to actual yayin nesech. But actual yayin nesech is a Biblical prohibition, as you already know their saying,12 "There are three categories of [prohibited] wine."13

The details of this mitzvah are explained in the final chapters of tractate Avodah Zorah.