Numbers 3:5 ASV

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

⁴  And Nadab and Abihu died before Jehovah, when they offered strange fire before Jehovah, in the wilderness of Sinai, and they had no children; and Eleazar and Ithamar ministered in the priest's office in the presence of Aaron their father.

⁵  And Jehovah spake unto Moses, saying,

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

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