Numbers 3:5-9

And the LORD spake unto Moses, saying,

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

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.

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.

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