Parsha Mitzvot: Shemini: Mitzvah 158 – Concept 321
“Do not drink intoxicating wine, you and your sons with you, when you come to the Tent of Meeting, that you not die; this is an eternal decree for your generations (Vayikra 10:9).” A Kohen must not enter the Temple intoxicated (Rambam Hilchot Bi’at ha-Mikdash – The Laws of Entering the Temple).
One who is serving God must act with great dignity. He must be completely focused on what he is doing. He must be prepared to derive lessons from his service, for which he will need a clear head.