Numbers 8:8

5 Yahweh spoke to Moses, saying,

6 Take the Levites from among the children of Israel, and cleanse them.

7 Thus shall you do to them, to cleanse them: sprinkle the water of expiation on them, and let them cause a razor to pass over all their flesh, and let them wash their clothes, and cleanse themselves.

8 Then let them take a young bull, and its meal-offering, fine flour mingled with oil; and another young bull shall you take for a sin- offering.

9 You shall present the Levites before the tent of meeting: and you shall assemble the whole congregation of the children of Israel:

10 and you shall present the Levites before Yahweh. The children of Israel shall lay their hands on the Levites:

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