Numbers 18:7-8

7And you and your sons with you shall guard your priesthood for all that concerns the altar and that is within the veil; and you shall serve. I give your priesthood as a gift, and any outsider who comes near shall be put to death."

8Then the Lord spoke to Aaron, "Behold, I have given you charge of the contributions made to me, all the consecrated things of the people of Israel. I have given them to you as a portion and to your sons as a perpetual due.