Numbers 18:23-24

²³To the sons alone of Levi, serving me in the tabernacle, and bearing the people’s sins, it shall be a lawful thing everlasting in your generations. (This is only for the sons of Levi, who serve me in the Tabernacle, and who bear the people’s sins; and this shall be an everlasting law in all your generations.)

²⁴They shall wield none other thing, and they shall be satisfied with the offering of tithes, which I separated into the uses and necessaries of them. (They shall possess nothing else, and they shall be satisfied with the offering of the tithes which I set apart for their uses and their necessities.)