Numbers 4:3

The period of active service for the Levites is here laid down as between 30 50 years of age. But in Numbers 8:23-26 it is between 25 50, though certain duties might be performed after that age. And in 1 Chronicles 23:24; 1 Chronicles 23:27; 2 Chronicles 31:17; Ezra 3:8 it begins at 20, and there is no upward limit of age. The statements appear to represent the customs that were current at three different periods.

the service This unusual meaning of the word which generally denotes -warfare" or -host" (R.V. marg.) is found again five times in this chapter (Numbers 4:23; Numbers 4:30; Numbers 4:35; Numbers 4:39; Numbers 4:43), and elsewhere only in Numbers 8:24 f., and of women in two very late passages, Exodus 38:8; 1 Samuel 2:22. It perhaps implies that the Levites formed an organized body appointed for God's work under the command of superior officials, as were the rest of Israel who were numbered for war.