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 1Ch 24:20-31; 1Ch 26:20-28).