Numbers 3:9

6 `Bring near the tribe of Levi, and thou hast caused it to stand before Aaron the priest, and they have served him,

7 and kept his charge, and the charge of all the company before the tent of meeting, to do the service of the tabernacle;

8 and they have kept all the vessels of the tent of meeting, and the charge of the sons of Israel, to do the service of the tabernacle;

9 and thou hast given the Levites to Aaron and to his sons; they are surely given to him out of the sons of Israel.

10 `And Aaron and his sons thou dost appoint, and they have kept their priesthood, and the stranger who cometh near is put to death.`

11 And Jehovah speaketh unto Moses, saying,

12 `And I, lo, I have taken the Levites from the midst of the sons of Israel instead of every first-born opening a womb among the sons of Israel, and the Levites have been Mine;