Courses
   When David was not permitted to build the temple, he proceeded,
   among the last acts of his life, with the assistance of Zadok
   and Ahimelech, to organize the priestly and musical services to
   be conducted in the house of God. (1.) He divided the priests
   into twenty-four courses (1 Chr. 24:1-19), sixteen being of the
   house of Eleazar and eight of that of Ithamar. Each course was
   under a head or chief, and ministered for a week, the order
   being determined by lot. (2.) The rest of the 38,000 Levites
   (23:4) were divided also into twenty-four courses, each to
   render some allotted service in public worship: 4,000 in
   twenty-four courses were set apart as singers and musicians
   under separate leaders (25); 4,000 as porters or keepers of the
   doors and gates of the sanctuary (26:1-19); and 6,000 as
   officers and judges to see to the administration of the law in
   all civil and ecclesiastical matters (20-32).
   
     This arrangement was re-established by Hezekiah (2 Chr. 31:2);
   and afterwards the four sacerdotal courses which are said to
   have returned from the Captivity were re-divided into the
   original number of twenty-four by Ezra (6:18).