Numbers 3:10

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.

¹¹  And the LORD spake unto Moses, saying,

¹²  And I, behold, I have taken the Levites from among the children of Israel instead of all the firstborn that openeth the matrix among the children of Israel: therefore the Levites shall be mine;