These were the sons of Levi, after the house of their fathers,.... According to the three classes of them, as descending from the three sons of Levi:
[even] the chief of the fathers; or heads of families:
as they were counted by number of names by their polls; or according to their heads, one by one:
that did the work for the service of the house of the Lord; the particulars of which are in 1 Chronicles 23:28
from the age of twenty years, and upwards; they were first numbered thirty and upwards, 1 Chronicles 23:3, but David before his death ordered they should be numbered from twenty and upwards, 1 Chronicles 23:27, because the Israelites being increased, there would be more work for the priests in the temple, which would require the assistance of more Levites. The reasons follow.