1 Chronicles 23:6

“And David divided them into courses among the sons of Levi, etc.] Into three classes, according to the number of them, which follow: namely, Gershon, Kohath, and Merari; (see <020616>Exodus 6:16).”

“David divided them into courses among the sons of Levi--These are enumerated according to their fathers' houses, but no more of these are mentioned here than the twenty-four thousand who were engaged in the work connected with the Lord's house. The fathers' houses of those Levites corresponded with the classes into which they [JOSEPHUS, Antiquities] as well as the priests were divided (see on Ch1 24:20-31; Ch1 26:20-28).”

“23:6-23 David divided the Levites into divisions according to their ancestral families. The number of available clerics far exceeded the requirements for a single Temple; the divisions provided a necessary time-sharing mechanism that enabled all the priests and Levites to serve in the Temple periodically (cp. Luke 1:5, 8).”

“divided: Ch2 8:14, Ch2 29:25, Ch2 31:2, Ch2 35:10; Ezr 6:18 courses: Heb. divisions, Ch1 24:1, Ch1 26:1 Gershon: Gershon, גרשׁון \[Strong's H1647\], is called גרשׁם \[Strong's H1648\], Gershom, in the parallel passage, simply by the mutation of נ, noon, into מ, mem. Ch1 6:1, Ch1 6:16, Gershom, Exo 6:16-24; Num 26:57, Num 26:58 1 Chronicles 23:7”

“The fathers'-houses of the Levites. - Ch1 23:6. "And David divided them into courses according to the sons of Levi, Gershon, Kohath, and Merari;" see on Ch1 6:1. The form ויּחלקם which recurs in Ch1 24:3 with the same pointing, is in more accurate MSS in that place pointed ויּחלקם. There are also found in MSS and editions ויחלּקם, and the rare form of the Kal ויּחלקם (for ויּחלקם); cf. J. H. Mich. Notae crit. This last pronunciation is attested for, Ch1 24:3, by D. Kimchi, who expressly remarks that the regular form ויּחלקם corresponds to it; cf. Norzi on this passage. Gesen. (in Thes. p. 483) and Ew. (83, c) regard ויּחלקם as a variety of the Piel (ויחלּקם), to which, however, Berth.…”