Numbers 3:2-4
2 The names of the sons of Aaron were Nadab the firstborn and Abihu, Eleazar and Ithamar.
3 Those were the names of Aaron’s sons, the anointed priests, who were ordained to serve as priests.
4 Nadab and Abihu, however, fell dead before the Lord when they made an offering with unauthorized fire before him in the Desert of Sinai. They had no sons; so only Eleazar and Ithamar served as priests during the lifetime of their father Aaron.