Numbers 18:9, 19

This shall be yours from the most holy gifts reserved from the fire; every offering of theirs, even every grain offering and every sin offering and every guilt offering, which they shall render to Me, shall be most holy for you and for your sons.

All the offerings of the holy gifts, which the sons of Israel offer to the LORD, I have given to you and your sons and your daughters with you, as a perpetual allotment. It is an everlasting covenant of salt before the LORD to you and your descendants with you.”