The Altar of Burnt-Offering: The Priests: Alone to Serve
Source: TTT
Numbers 18:3, 7
And they shall attend to your duties and to all the duties of the Tent; but they must not come near to the furnishings of the sanctuary or the altar, or both they and you will die. / But only you and your sons shall attend to your priesthood for everything concerning the altar and what is inside the veil, and you are to perform that service. I am giving you the work of the priesthood as a gift, but any outsider who comes near the sanctuary must be put to death.”