Zevachim 16 - 22
Drinking and Duchening
“Rav would not teach Torah publicly after eating and drinking during a Yom Tov meal until the next day due to not being completely sober.”
The mishna teaches numerous factors that would invalidate the service in the Beit Hamikdash. For example: if the kohen was lacking in the number of garments required, or if he was sitting down. A case that is not mentioned in the mishna, but is taught in the gemara, is the service of a kohen who drank wine is invalid. Initially, the gemara thought to prove this halacha from the verses: “Do not drink wine that will lead to intoxication, neither you nor your sons with you, when you go into the Mikdash … to distinguish between the holy and the profane.” (Vayikra 10:9-10) Rashi in our sugya explains this to mean that “service that you do while inebriated is called profane (i.e. invalid).” Rashi on Chumash also explains in this manner.
However, the gemara concludes that the source for “drunken service” being invalid is actually a gezeira shava derivation from the case of a kohen lacking the proper number of garments. So what do the verses in Vayikra in fact teach? That a person should not render a halachic ruling when not completely sober, as in the case of Rav who refrained from teaching after a Yom Tov meal that included wine. According to this interpretation, the two verses in Vayikra are not both speaking about the Beit Hamikdash and sobriety. Rather, the second verse comes to teach that when teaching distinctions in halacha — “between the holy and the profane” — one must be sober. (Shulchan Aruch Orach Chaim 242:13)
Another halacha regarding sobriety is that a kohen who has drunk a revi’it of wine may not duchen (say the Priestly Blessing). Since duchening is comparable to the service in the Beit Hamikdash, and service in the Beit Hamikdash requires sobriety, so does duchening. (Shulchan Aruch Orach Chaim 128:38)
- Zevachim 17b, 18a