Numbers 3:2-4

2The names of Aaron’s sons were Nadab (the oldest), Abihu, Eleazar, and Ithamar.

3These sons of Aaron were anointed and ordained to minister as priests.

4But Nadab and Abihu died in the Lord’s presence in the wilderness of Sinai when they burned before the Lord the wrong kind of fire, different than he had commanded. Since they had no sons, this left only Eleazar and Ithamar to serve as priests with their father, Aaron.