NumbersChapter 8

"Speak to Aaron and tell him: When you set up the lamps, the seven lamps are to give light toward the front of the lampstand."
This was how the lampstand was made: hammered gold from its base to its blossoms, hammered work throughout. It was made according to the pattern the LORD had shown Moses.
This is what you are to do to cleanse them: sprinkle them with the water of purification; then have them shave their whole bodies and wash their clothes, and so they will be clean.
They are to take a young bull with its grain offering of fine flour mixed with oil, and you are to take a second young bull for a sin offering.
Bring the Levites to the front of the tent of meeting and assemble the whole community of Israel.
Present the Levites before the LORD, and the Israelites are to lay their hands on them.
Then Aaron shall offer the Levites before the LORD as a wave offering from the Israelites, and they shall then do the service of the LORD.
The Levites are to lay their hands on the heads of the bulls; then offer one as a sin offering and the other as a burnt offering to the LORD, to make atonement for the Levites.
After you have cleansed them and presented them as a wave offering, the Levites are to come and do their work at the tent of meeting.
They are wholly given over to me from among the Israelites. I have taken them as my own in place of every firstborn, everyone who opens the womb among the Israelites.
For every firstborn among the Israelites is mine, both human and animal. On the day I struck down every firstborn in the land of Egypt, I set them apart for myself.
From among the Israelites I have given the Levites as a gift to Aaron and his sons, to carry out the service of the Israelites at the tent of meeting and to make atonement for them, so that no plague will strike the Israelites when they come near the sanctuary."
Moses, Aaron, and the whole community of Israel did with the Levites exactly as the LORD had commanded Moses concerning them; that is what the Israelites did for them.
The Levites purified themselves and washed their clothes. Then Aaron presented them as a wave offering before the LORD and made atonement for them to cleanse them.
After that, the Levites came to do their work at the tent of meeting under the supervision of Aaron and his sons. They did with the Levites just as the LORD had commanded Moses.
"This is the rule for the Levites: from the age of twenty-five and upward a man shall enter the ranks of those who serve at the tent of meeting.
He may assist his brothers at the tent of meeting by keeping watch, but he is not to do the work himself. This is how you are to assign the duties of the Levites."