One of the various charges God gave to the Old Testament priesthood of Israel (descendants of Aaron) was this: “Do not drink wine or intoxicating drink, you, nor your sons with you, when you go into the tabernacle of meeting [with the LORD] , lest you die. It shall be a statute throughout your generations” (Leviticus 10:9).
Why did God give this charge to the priests? He told them: so “…that you may distinguish between holy and unholy, and between unclean and clean, and that you may teach the children of Israel all the statutes which the LORD has spoken to them by the hand of Moses” (Verses 10-11).