Numbers 8:6-11, 21

“Now set the Levites apart from the rest of the people of Israel and make them ceremonially clean. Do this by sprinkling them with the water of purification, and have them shave their entire body and wash their clothing. Then they will be ceremonially clean. Have them bring a young bull and a grain offering of choice flour moistened with olive oil, along with a second young bull for a sin offering. Then assemble the whole community of Israel, and present the Levites at the entrance of the Tabernacle. When you present the Levites before the LORD, the people of Israel must lay their hands on them. Raising his hands, Aaron must then present the Levites to the LORD as a special offering from the people of Israel, thus dedicating them to the LORD’s service.

The Levites purified themselves from sin and washed their clothes, and Aaron lifted them up and presented them to the LORD as a special offering. He then offered a sacrifice to purify them and make them right with the LORD.