Numbers 3:2-4 NIV

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

References for Numbers 3:2

3 Those were the names of Aaron’s sons, the anointed priests, who were ordained to serve as priests.

References for Numbers 3:3

4 Nadab and Abihu, however, died before the LORD when they made an offering with unauthorized fire before him in the Desert of Sinai. They had no sons, so Eleazar and Ithamar served as priests during the lifetime of their father Aaron.

References for Numbers 3:4