הלכה אויף במדבר 18:4

That an intoxicated person shall not enter the Sanctuary, nor give decisions in matters of the Law, as it is said, “Do not drink wine nor strong drink…. when ye go into the Tabernacle…. and that ye may teach the children of Israel” (Lev. 10:9-11).

That one, not a descendant of Aaron in the male line, shall not serve (in the Sanctuary), as it is said, “And a stranger shall not come nigh unto you” (Num. 18:4-7).

The commandment to guard the Temple: That the priests and the Levites were commanded to guard the Temple and walk around it constantly the whole night, on each and every night (see R. Chaim Heller — Sefer HaMitzvot, Positive Commandments 22) — and this guarding is to honor it, to exalt it and to glorify it, and not from there being any fear of the enemy, God forbid — as it is stated (Numbers 18:4), “and they shall guard the guarding of the Tent of Meeting.” And the language of Sifrei Bamidbar 116 is “‘And you and your sons with you will be in front of the Tent of Testimony’ (Numbers 18:2) — the priests inside and the Levites only outside”; meaning to say to guard it and to walk around it. And in the Mekhilta (Sifrei Zuta on Numbers 18:4), they said, “‘And they shall guard the guarding of the Tent of Meeting’ — I only know of a positive commandment, etc.” Behold, it is elucidated that its guarding is a positive commandment. And there it says another greatness of the Temple is that it has guards — “A palace that has guards is not similar to a palace that does not have guards.” And it is known that the palace is a name for the sanctuary.