New American Standard Bible (NASB)
Numbers 2
33 The Levites, however, were not numbered among the sons of Israel, just as the Lord had commanded Moses.
34 Thus the sons of Israel did; according to all that the Lord commanded Moses, so they camped by their standards, and so they set out, every one by his family according to his father’s household.
Numbers 3
1 Now these are the records of the generations of Aaron and Moses at the time when the Lord spoke with Moses on Mount Sinai.
2 These then 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 strange 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 their father Aaron.
5 Then the Lord spoke to Moses, saying,
6 "Bring the tribe of Levi near and set them before Aaron the priest, that they may serve him.
7 They shall perform the duties for him and for the whole congregation before the tent of meeting, to do the service of the tabernacle.
8 They shall also keep all the furnishings of the tent of meeting, along with the duties of the sons of Israel, to do the service of the tabernacle.
9 You shall thus give the Levites to Aaron and to his sons; they are wholly given to him from among the sons of Israel.