2 Chronicles 8:14
And he appointed, according to the order of David his father, the courses of the priests to their service, and the Levites to their charges, to praise and minister before the priests, as the duty of every day required: the porters also by their courses at every gate: for so had David the man of God commanded.
Torrey's Topical Textbook—AKJV

2 Chronicles 31:17
Both to the genealogy of the priests by the house of their fathers, and the Levites from twenty years old and upward, in their charges by their courses;
Torrey's Topical Textbook—AKJV