Numbers 8 (Vespers - Meeting of Our Lord)
Now the LORD said to Moses, "Say to Aaron, When you set up the lamps, the seven lamps shall give light in front of the lampstand." And Aaron did so; he set up its lamps to give light in front of the lampstand, as the LORD commanded Moses. And this was the workmanship of the lampstand, hammered work of gold; from its base to its flowers, it was hammered work; according to the pattern which the LORD had shown Moses, so he made the lampstand. And the LORD said to Moses, "Take the Levites from among the people of Israel, and cleanse them. And thus you shall do to them, to cleanse them: sprinkle the water of expiation upon them, and let them go with a razor over all their body, and wash their clothes and cleanse themselves. Then let them take a young bull and its cereal offering of fine flour mixed with oil, and you shall take another young bull for a sin offering. And you shall present the Levites before the tent of meeting, and assemble the whole congregation of the people of Israel. When you present the Levites before the LORD, the people of Israel shall lay their hands upon the Levites, and Aaron shall offer the Levites before the LORD as a wave offering from the people of Israel, that it may be theirs to do the service of the LORD. Then the Levites shall lay their hands upon the heads of the bulls; and you shall offer the one for a sin offering and the other for a burnt offering to the LORD, to make atonement for the Levites. And you shall cause the Levites to attend Aaron and his sons, and shall offer them as a wave offering to the LORD. "Thus you shall separate the Levites from among the people of Israel, and the Levites shall be mine. And after that the Levites shall go in to do service at the tent of meeting, when you have cleansed them and offered them as a wave offering. For they are wholly given to me from among the people of Israel; instead of all that open the womb, the first-born of all the people of Israel, I have taken them for myself. For all the first-born among the people of Israel are mine, both of man and of beast; on the day that I slew all the first-born in the land of Egypt I consecrated them for myself, and I have taken the Levites instead of all the first-born among the people of Israel. And I have given the Levites as a gift to Aaron and his sons from among the people of Israel, to do the service for the people of Israel at the tent of meeting, and to make atonement for the people of Israel, that there may be no plague among the people of Israel in case the people of Israel should come near the sanctuary." Thus did Moses and Aaron and all the congregation of the people of Israel to the Levites; according to all that the LORD commanded Moses concerning the Levites, the people of Israel did to them. And the Levites purified themselves from sin, and washed their clothes; and Aaron offered them as a wave offering before the LORD, and Aaron made atonement for them to cleanse them. And after that the Levites went in to do their service in the tent of meeting in attendance upon Aaron and his sons; as the LORD had commanded Moses concerning the Levites, so they did to them. And the LORD said to Moses, "This is what pertains to the Levites: from twenty-five years old and upward they shall go in to perform the work in the service of the tent of meeting; and from the age of fifty years they shall withdraw from the work of the service and serve no more, but minister to their brethren in the tent of meeting, to keep the charge, and they shall do no service. Thus shall you do to the Levites in assigning their duties."