2CH 8:14

14 And he appointed, according to the mishpat Dovid Aviv, the machlekot [(divisions)] of the Kohanim to their avodah service, and the Levi'im to their mishmerot [(watches)], to praise and minister before the Kohanim, as the requirement of every yom required; the Sho'arim [(Gatekeepers)] also by their machlekot [(divisions)] at every sha'ar; for thus was the mitzvot Dovid Ish HaElohim.