Numbers 18:1; Numbers 18:7

1 So the LORD said to Aaron, "You and your sons and your father's house with you shall bear iniquity connected with the sanctuary, and you and your sons with you shall bear iniquity connected with your priesthood.

7 And 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."