Numbers 18:8, 19

Then the LORD said to Aaron, “I myself have put you in charge of the offerings presented to me; all the holy offerings the Israelites give me I give to you and your sons as your portion, your perpetual share.

Whatever is set aside from the holy offerings the Israelites present to the LORD I give to you and your sons and daughters as your perpetual share. It is an everlasting covenant of salt before the LORD for both you and your offspring.”