Adam Clarke on Leviticus 10:10

That we may put difference between holy and unholy - This is a strong reason why they should drink no inebriating liquor, that their understanding being clear, and their judgment correct, they might be always able to discern between the clean and the unclean, and ever pronounce righteous judgment. Injunctions similar to this were found among the Egyptians, Carthaginians, and Greeks. Indeed, common sense itself shows that neither a drunkard nor a sot should ever be suffered to minister in holy things.