Numbers 3:2-4

2The names of the sons of Aaron were Nadab, Abihu, Eleazar and Ithamar. Nadab was the firstborn son.

3Aaron anointed them, and he gave authority to them to work as priests.

4But Nadab and Abihu fell down and died in front of the Lord. That happened when they offered strange fire to the Lord in the Sinai desert. They had no children. So only Eleazar and Ithamar worked as priests while their father Aaron was alive.