John Gill Bible Commentary

In the number of all the males, from a month old and upwards, were eight thousand and six hundred,.... 8,600 men, which was the largest number of any of the houses of the Levites; but considering it had double the number of families in it, the increase was not so large in proportion, at least to Gershon, whose two families wanted but 1,100 of these four: keeping the charge of the sanctuary; of the holy and most holy places, and the vessels and instruments belonging thereunto; not that the males of a month old were keeping them, but when they were grown up and were capable of it, they had the charge thereof, in which they were instructed and trained up from their youth.