The number of all the males a month old or more was 8,600. They were responsible for the duties of the sanctuary.
The Levites being granted to Aaron to minister to him, they are here delivered to him by tale, that he might know what he had, and employ them accordingly. Observe, I. By what rule they were numbered: Every male from a month old and upward, Num 3:15.
Commenting on Numbers 3:14-39
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...
In the number of all the males, from a month old and upward, [were] eight thousand and six hundred, keeping the charge of the sanctuary. (k) Everyone doing his duty in the sanctuary.