Numbers 18:5-7

5“You must be in charge of the work done at the holy place and at the altar. Then I won’t show my anger against the Israelites again.

6I have chosen the other Levites from among the Israelites to help you. They are a gift given to the Lord to do whatever work is necessary at the tent of meeting.

7Only you and your sons may do the work of priests—everything done at the altar and under the canopy. This is my gift to you: You may serve me as priests. Anyone else who comes near ⌞the holy place to do this work⌟ must die.”