Numbers 18:3, 7

They are to perform duties for you and for the whole tent. They must not come near the sanctuary equipment or the altar; otherwise, both they and you will die.

But you and your sons will carry out your priestly responsibilities  for everything concerning the altar and for what is inside the curtain, and you will do that work. I am giving you the work of the priesthood as a gift,  but an unauthorized person who comes near the sanctuary will be put to death.”