How the lamps are to be lit, 1-4. The consecration of the Levites, 5-22. The age and time of their service, 23-26.
1 And the LORD spoke to Moses, saying, 2 "Speak to Aaron and say to him, 'When you light the lamps, the seven lamps shall give light over against the candlestick.'" 3 And Aaron did so. He lit its lamps over against the candlestick, as the LORD commanded Moses. 4 And this work of the candlestick was of beaten gold, to its shaft, to its flowers, was beaten work. According to the pattern which the LORD had shown Moses, so he made the candlestick.
5 And the LORD spoke to Moses, saying, 6 "Take the Levites from among the children of Israel and cleanse them. 7 And thus you shall do to them to cleanse them: sprinkle water of purifying upon them, and let them shave all their flesh and wash their clothes, and so make themselves clean. 8 Then let them take a young bull with his food-offering, even fine flour mingled with oil, and another young bull you shall take for a sin-offering. 9 And you shall bring the Levites before the Tabernacle of the Congregation and you shall convene the whole assembly of the children of Israel. 10 And you shall bring the Levites before the LORD, and the children of Israel shall put their hands upon the Levites. 11 And Aaron shall offer the Levites before the LORD for an offering of the children of Israel so that they may execute the service of the LORD. 12 And the Levites shall lay their hands upon the heads of the bulls. And you shall offer one for a sin-offering and the other for a burnt-offering to the LORD to make an atonement for the Levites. 13 And you shall set the Levites before Aaron and before his sons and offer them for an offering to the LORD.
14 "Thus you shall separate the Levites from among the children of Israel, and the Levites shall be mine. 15 And after that the Levites shall go in to perform the service of the Tabernacle of the Congregation. And you shall cleanse them and offer them for an offering, 16 For they are wholly given to me from among the children of Israel. Instead of those who open every womb, even instead of the first-born of all the children of Israel, I have taken them for myself, 17 For all the first born of the children of Israel are mine, both man and beast. On the day that I smote every first-born in the land of Egypt I sanctified them for myself. 18 And I have taken the Levites for all the first-born of the children of Israel. 19 And I have given the Levites as a gift to Aaron and to his sons from among the children of Israel, to do the service of the children of Israel in the Tabernacle of the Congregation and to make an atonement for the children of Israel, so that there may be no plague among the children of Israel when the children of Israel come near to the sanctuary."
20 And Moses, Aaron, and all the congregation of the children of Israel did to the Levites according to all that the LORD commanded Moses concerning the Levites. And the children of Israel did so to them. 21 And the Levites were purified and they washed their clothes. And Aaron offered them as an offering before the LORD. And Aaron made an atonement for them to cleanse them. 22 And after that the Levites went in to perform their service in the Tabernacle of the Congregation before Aaron and before his sons. As the LORD had commanded Moses concerning the Levites, so they did to them.
23 And the LORD spoke to Moses, saying, 24 "This is that which belongs to the Levites: from twenty-five years old and upward they shall go in to wait upon the service of the Tabernacle of the Congregation, 25 And from the age of fifty years they shall cease waiting upon its service and shall serve no more, 26 But shall minister with their brothers in the Tabernacle of the Congregation to keep the charge and shall do no service. Thus you shall do to the Levites concerning their charge."
Matthew Henry Commentary - Numbers, Chapter 8[➚]
[v.17] - Reference, Exodus 13:2.