Numbers 18:22-23

²²that the sons of Israel nigh no more to the tabernacle of the bond of peace, neither do deadly sin. (so that the Israelites no longer come near to the Tabernacle of the Covenant, and so do sin, and then must die.)

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.)