Numbers 18:19

18:19 All the raised offerings of the holy things that the Israelites offer to the Lord, I have given to you, and to your sons and daughters with you, as a perpetual ordinance. It is a covenant of salt forever before the Lord for you and for your descendants with you.”

Numbers 18:24

18:24 But I have given to the Levites for an inheritance the tithes of the Israelites that are offered to the Lord as a raised offering. That is why I said to them that among the Israelites they are to have no inheritance.”