Numbers 3:5-9

5And the Lord spoke to Moses, saying:

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

7And they shall attend to his needs and the needs of the whole congregation before the tabernacle of meeting, to do the work of the tabernacle.

8Also they shall attend to all the furnishings of the tabernacle of meeting, and to the needs of the children of Israel, to do the work of the tabernacle.

9And you shall give the Levites to Aaron and his sons; they are given entirely to him from among the children of Israel.