Numbers 3:8

⁶  Bring the tribe of Levi near, and present them before Aaron the priest, that they may minister unto him.

⁷  And they shall keep his charge, and the charge of the whole congregation before the tabernacle of the congregation, to do the service of the tabernacle.

⁸  And they shall keep all the instruments of the tabernacle of the congregation, and the charge of the children of Israel, to do the service of the tabernacle.

⁹  And thou shalt give the Levites unto Aaron and to his sons: they are wholly given unto him out of the children of Israel.

¹⁰  And thou shalt appoint Aaron and his sons, and they shall wait on their priest's office: and the stranger that cometh nigh shall be put to death.