Numbers 8:12
And the Levites shall lay their hands upon the heads of the bullocks: and thou shalt offer the one for a sin offering, and the other for a burnt offering, unto the LORD, to make an atonement for the Levites. And the Levites shall lay their hands upon the heads of the bullocks: and thou shalt offer the one for a sin offering, and the other for a burnt offering, unto the LORD, to make an atonement for the Levites.
The rite belongs to the consecration of the Levites for sanctuary service. In it the Levites laid their hands upon the heads of two bullocks. One bullock was offered as a sin offering and the other as a burnt offering unto the LORD. Those offerings made atonement for the Levites and completed their dedication to sanctuary service.