Numbers 18:6-8

New Century Version

⁶ I myself chose your fellow Levites from among the Israelites as a gift given for you to the Lord, to work at the Meeting Tent. ⁷ But only you and your sons may serve as priests. Only you may serve at the altar or go behind the curtain. I am giving you this gift of serving as a priest, and anyone else who comes near the Holy Place will be put to death.”

⁸ Then the Lord said to Aaron, “I myself make you responsible for the offerings given to me. All the holy offerings that the Israelites give to me, I give to you and your sons as your share, your continual portion.