When the Levites had purified themselves and washed their garments, Aaron presented them as an elevated offering before the Lord, and made atonement for them to cleanse them.
The priest who performs the purification ceremony shall place the person who is being purified, as well as all these offerings, before the Lord at the entrance of the tent of meeting.
they shall purify themselves with the water on the third and on the seventh day, and then be clean. But if they fail to purify themselves on the third and on the seventh day, they will not become clean.
The clean will sprinkle the unclean on the third and on the seventh day, and thus purify them on the seventh day. Then they will wash their garments and bathe in water, and in the evening be clean.
This, then, is what Moses and Aaron and the whole community of the Israelites did with respect to the Levites; the Israelites did exactly as the Lord had commanded Moses concerning them.
Only then did they enter upon their service in the tent of meeting under the supervision of Aaron and his sons. Exactly as the Lord had commanded Moses concerning the Levites, so it was done with regard to them. Age Limits for Levitical Service.
This is what you shall do to them to cleanse them. Sprinkle them with the water of purification, have them shave their whole bodies and wash their garments, and so cleanse themselves.