Numbers 3:10

3:10 So you are to appoint Aaron and his sons, and they will be responsible for their priesthood; but the unauthorized person who comes near must be put to death.”

Numbers 18:1

Responsibilities of the Priests

18:1 The Lord said to Aaron, “You and your sons and your tribe with you must bear the iniquity of the sanctuary, and you and your sons with you must bear the iniquity of your priesthood.

Numbers 25:13

25:13 So it will be to him and his descendants after him a covenant of a permanent priesthood, because he has been zealous for his God, and has made atonement for the Israelites.’”

Numbers 18:7

18:7 But you and your sons with you are responsible for your priestly duties, for everything at the altar and within the curtain. And you must serve. I give you the priesthood as a gift for service; but the unauthorized person who approaches must be put to death.”