Charles Ellicott Commentary 1 Chronicles 23:6

"And David divided them into courses according to the sons of Levi: Gershon, Kohath, and Merari." — 1 Chronicles 23:6 (ASV)

And David divided them into courses. —Heb., he divided him them (reflexive form of verb, with suffix) into divisions. (Compare to 1 Chronicles 24:3 and Genesis 14:15.) Others read the simple voice of the verb here, as in 1 Chronicles 24:4–5, 2 Chronicles 23:18, and Nehemiah 9:22; still others read the intensive voice, as in 1 Chronicles 16:3 (only). It is a question of pointing, as the consonants remain the same in each form. “David divided them”—i.e., the 2,400 superintendents (1 Chronicles 23:4; compare to 1 Chronicles 23:24). Many of the names enumerated here recur in 1 Chronicles 24:20–31 and 1 Chronicles 26:20–28, whereas the names of the courses of musicians (1 Chronicles 25:1–31), warders (1 Chronicles 26:1–19), and scribes and judges (1 Chronicles 26:29–32) are totally different.

Among the sons of Levi. —Rather, according to the sons of Levi, namely, according to Gershon, etc.: that is, according to the three great subdivisions of the tribe (1 Chronicles 6:1; 1 Chronicles 6:16). Notice the correct spelling, “Gershon” (not Gershom).