Numbers 3:5 WBT

³  These [are] the names of the sons of Aaron, the priests who were anointed, whom he consecrated to minister in the priest's office.

⁴  And 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: and Eleazar and Ithamar ministered in the priest's office in the sight of Aaron their father.

⁵  And the LORD spoke to Moses, saying,

⁶  Bring the tribe of Levi near, and present them before Aaron the priest, that they may minister to him.

⁷  And they shall keep his charge, and the charge of the whole congregation before the tabernacle of the congregation, to do the service of the tabernacle.