Rashi on Leviticus
ולהבדיל AND TO DISTINGUISH [BETWEEN THE HOLY AND THE UNHOLY] — i. e., Observe this law in order that ye may be able to distinguish between a holy (valid) sacrificial act and one which has become profane (invalid). Thus you may learn that if one performed a sacrificial rite in a state of intoxication his ministry was invalid (Sifra, Shemini, Section 1 8; Zevachim 17b).
Sforno on Leviticus
ולהבדיל..ולהורות. We know from Hoseah 4,11 that “wine and new wine destroy the minds of My people.” Issuing decrees, verdicts or religious rulings while intoxicated is therefore not tolerable. Solomon, in Proverbs 31,4-5 is similarly critical of such a practice writing: “wine is not for kings, O Lemuel; not for kings to drink, nor any strong drink for princes, lest they drink and forget what has been ordained.”
Rashbam on Leviticus
ולהבדיל ולהורות, as our sages said that a judge or teacher in state of intoxication must not issue any halachic rulings. (Eyruvin 64).