Musar zu Wajikra 10:9

“Drink no wine or other intoxicant, etc. And to distinguish between the holy and the profane, etc. And you must teach the Israelites” (Leviticus 10:9-11). And our Rabbis, may their memory be blessed, said (Eruvin 64a), “If one drank a quarter [log] of wine that was not mixed with water, he may not issue a ruling, but if he drink more than a quarter, he may not issue a ruling even though he mixed it [with water].

Our sages in Vayikra Rabbah 20,5 claim that one of the reasons the two sons of Aaron died was that they entered the Sanctuary while intoxicated by wine. This is a veiled reference to the יין המשומר, the wine stemming from גן עדן, which we have frequently discussed, as being instrumental in their death. This is why the Torah reports the legislation that priests must not enter the Sanctuary after having drunk wine or other intoxicating drink. If the priests want to benefit from the יין המשומר in the World to Come, they must refrain from drinking the intoxicating drinks of this world while performing service in the Temple.