Now the Levites were numbered from the age of thirty years and upward: and their number by their polls, man by man, was thirty and eight thousand. (1 Chronicles 23:3)
Levites from the ages of 30 to 50 were to be employed in the “service of the ministry, and the service of the burden in the tabernacle of the congregation” (Num. 4:47). According to Num. 8:23-25 the Lord specifically prescribed that those who should “go in to wait upon the service of the tabernacle” should be from 25 to 50 years of age. Perhaps this latter group included those engaged in the manual services connected with the sanctuary. The former group probably consisted of those who engaged in the more sacred priestly services.
Were numbered.
The Levites were not numbered at the time of David’s census of men of military age (ch. 21:6). But for the purpose of making arrangements for the conduct of all phases of the work of the realm a census of the Levites would be necessary.