Numbers 3:9

6 Bring the tribe of Levi near, and set 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 tent of meeting, to do the service of the tabernacle.

8 And they shall keep all the furniture of the tent of meeting, 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 on the behalf of the children of Israel.

10 And thou shalt appoint Aaron and his sons, and they shall keep their priesthood: and the stranger that cometh nigh shall be put to death.

11 And Jehovah spake unto Moses, saying,

12 And I, behold, I have taken the Levites from among the children of Israel instead of all the first-born that openeth the womb among the children of Israel; and the Levites shall be mine: