Numbers 8:5-8

5And the LORD spake unto Moses, saying,

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

7And thus shalt thou do unto them, to cleanse them: sprinkle the water of expiation upon them, and let them cause a razor to pass over all their flesh, and let them wash their clothes, and cleanse themselves.

8Then let them take a young bullock, and its meal offering, fine flour mingled with oil, and another young bullock shalt thou take for a sin offering.