I Chronicles 23:3

Now the Levites were numbered from the age of thirty years, and upward,.... So they were numbered in the days of Moses, and by his order, and so they were now at first; though afterwards there was a new reckoning of them, Ch1 23:24. and their number by their posts; or, according to their heads: man by man, was thirty and eight thousand; which vastly exceeds the number in the times of Moses; see Num 4:47, but then those above fifty years of age were not numbered, as they now might; since their work in the temple would be much more easy, no burdens to carry, as the ark, the vessels, &c.

David, having given charge concerning the building of the temple, in this and the following chapters settles the method of the temple-service and puts into order the offices and officers of it. In the late irregular times, and during the wars in the beginning of his reign, we may suppose that, though the Levitical ordinances were kept up, yet it was not in the order, nor with the beauty and exactness, that were desirable. Now David, being a prophet, as well as a prince, by divine warrant and direction, "set in order the things that were wanting." In this chapter we are informed, I. He declared Solomon to be his successor, (Ch1 23:1). II. He numbered the Levites, and appointed them to their respective offices (Ch1 23:2-5). III. He took an account of the several families of the Levites (v. 6-23). IV. He made a new reckoning of them from twenty years old, and appointed them their work (Ch1 23:24-32). And in this he prepared for the temple as truly as when he laid up gold and silver for it; for the place is of small account in comparison with the work.

23:3-5 The Levites are recorded according to their roles rather than their families.