Numbers 8:19

8:19 I have given the Levites as a gift to Aaron and his sons from among the Israelites, to do the work for the Israelites in the tent of meeting, and to make atonement for the Israelites, so there will be no plague among the Israelites when the Israelites come near the sanctuary.”

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.”

Numbers 18:11

18:11 “And this is yours: the raised offering of their gift, along with all the wave offerings of the Israelites. I have given them to you and to your sons and daughters with you as a perpetual ordinance. Everyone who is ceremonially clean in your household may eat of it.