3:1 These are the generations of Aaron and Moses at the time when the Lord spoke with Moses on Mount Sinai. 2 These are the names of the sons of Aaron: Nadab the firstborn, and Abihu, Eleazar, and Ithamar. 3 These are the names of the sons of Aaron, the anointed priests, whom he ordained to serve as priests. 4 But Nadab and Abihu died before the Lord when they offered unauthorized fire before the Lord in the wilderness of Sinai, and they had no children. So Eleazar and Ithamar served as priests in the lifetime of Aaron their father.

5 And the Lord spoke to Moses, saying, 6 “Bring the tribe of Levi near, and set them before Aaron the priest, that they may minister to him. 7 They shall keep guard over him and over the whole congregation before the tent of meeting, as they minister at the tabernacle. 8 They shall guard all the furnishings of the tent of meeting, and keep guard over the people of Israel as they minister at the tabernacle. (ESV)

11 And the Lord spoke to Moses, saying, 12 “Behold, I have taken the Levites from among the people of Israel instead of every firstborn who opens the womb among the people of Israel. The Levites shall be mine, 13 for all the firstborn are mine. On the day that I struck down all the firstborn in the land of Egypt, I consecrated for my own all the firstborn in Israel, both of man and of beast. They shall be mine: I am the Lord.” (ESV)

39 All those listed among the Levites, whom Moses and Aaron listed at the commandment of the Lord, by clans, all the males from a month old and upward, were 22,000.

40 And the Lord said to Moses, “List all the firstborn males of the people of Israel, from a month old and upward, taking the number of their names. 41 And you shall take the Levites for me—I am the Lord—instead of all the firstborn among the people of Israel, and the cattle of the Levites instead of all the firstborn among the cattle of the people of Israel.” 42 So Moses listed all the firstborn among the people of Israel, as the Lord commanded him. 43 And all the firstborn males, according to the number of names, from a month old and upward as listed were 22,273.

44 And the Lord spoke to Moses, saying, 45 “Take the Levites instead of all the firstborn among the people of Israel, and the cattle of the Levites instead of their cattle. The Levites shall be mine: I am the Lord. 46 And as the redemption price for the 273 of the firstborn of the people of Israel, over and above the number of the male Levites, 47 you shall take five shekels per head; you shall take them according to the shekel of the sanctuary (the shekel of twenty gerahs), 48 and give the money to Aaron and his sons as the redemption price for those who are over.” 49 So Moses took the redemption money from those who were over and above those redeemed by the Levites. 50 From the firstborn of the people of Israel he took the money, 1,365 shekels, by the shekel of the sanctuary. 51 And Moses gave the redemption money to Aaron and his sons, according to the word of the Lord, as the Lord commanded Moses. (ESV)