Numbers 3:4

²  And 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 priests which 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 spake unto Moses, saying,

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