Charles Ellicott Commentary 1 Chronicles 24:2

"But Nadab and Abihu died before their father, and had no children: therefore Eleazar and Ithamar executed the priest`s office." — 1 Chronicles 24:2 (ASV)

But Nadab and Abihu died before their father. —Leviticus 10:1–2 tells why: namely, because they offered strange fire before the Lord. (See also Numbers 3:4, from which our text appears to be derived.)

And had no children. — Literally, and sons had not come to be to them (that is, had not been born to them).

Therefore Eleazar and Ithamar. — And Eleazar and Ithamar acted as priests; Numbers adds, before the face of Aaron their father. It is implied that the office of the priesthood remained with the two lines, or houses, of Eleazar and Ithamar.