John Gills Exposition of the Bible Commentary - 1 Chronicles 24:31
These likewise cast lots over against their brethren, the sons of Aaron ,.... These, being divided into twenty four classes also, cast lots, which class should answer to, attend upon, and serve the first course of the priests, and which the second, and so on. And this they did in the same solemn and public manner as the priests had done: in the presence of David the king, and Zadok, and Ahimelech, and the chief of the fathers of the priests and Levites ; as in 1 Chronicles 24:6 . ... read more
Matthew Henry's Complete Commentary - 1 Chronicles 24:20-31
Most of the Levites here named were mentioned before, 1 Chron. 23:16-23 They were of those who were to attend the priests in the service of the house of God. But they are here mentioned again as heads of the twenty-four courses of Levites (and about so many are here named), who were to attend the twenty-four courses of the priests: they are therefore said to cast lots over against their brethren (so they are called, not their lords), the sons of Aaron, who were not to lord it over God's... read more