Charles Ellicott Commentary 1 Chronicles 24:1

"And the courses of the sons of Aaron [were these]. The sons of Aaron: Nadab and Abihu, Eleazar and Ithamar." — 1 Chronicles 24:1 (ASV)

Now these are the divisions. —Literally, And for the sons of Aaron, their divisions (were as follows). The sentence forms a superscription to the section (1 Chronicles 24:1–19).

The sons of Aaron are named above (1 Chronicles 6:3). (Compare to Exodus 6:23.) As usual, the writer starts from the very beginning.