And he appointed, according to the order of David his father, the courses of the priests to their service,.... The twenty four courses which served weekly in their turns, Ch1 24:1. and the Levites to their charges, to praise and minister before the priests, as duty of every day required; who also had their courses by lot, to sing the praises of God, when the priests sacrificed, or blew the trumpets, Ch1 25:1, the porters also by their courses at every gate; from hence Dr. Lightfoot concludes that these were divided into twenty four classes, as the priests and Levite singers were: for so had David the man of God commanded, Ch1 26:1, who in all these affairs acted as a prophet, under the inspiration and direction of the Holy Spirit of God.