Numbers 8:13

10 and thou shalt present the Levites before Jehovah. And the children of Israel shall lay their hands upon the Levites:

11 and Aaron shall offer the Levites before Jehovah for a wave-offering, on the behalf of the children of Israel, that it may be theirs to do the service of Jehovah.

12 And the Levites shall lay their hands upon the heads of the bullocks: and offer thou the one for a sin-offering, and the other for a burnt-offering, unto Jehovah, to make atonement for the Levites.

13 And thou shalt set the Levites before Aaron, and before his sons, and offer them for a wave-offering unto Jehovah.

14 Thus shalt thou separate the Levites from among the children of Israel; and the Levites shall be mine.

15 And after that shall the Levites go in to do the service of the tent of meeting: and thou shalt cleanse them, and offer them for a wave-offering.

16 For they are wholly given unto me from among the children of Israel; instead of all that openeth the womb, even the first-born of all the children of Israel, have I taken them unto me.