From twenty and five years old and upward. A short time before the minimum age had been fixed at thirty (Numbers 4:3). That direction, however, concerned the transport of the tabernacle and its belongings; this was a permanent regulation designed for the ordinary labours of the sanctuary at a time when the Levites would be scattered throughout their cities, and could only serve by courses.
For the latter purpose many more would be required; and indeed they were found insufficient as it was in the latter days of David, when the wealth and devotion of the kingdom were fast increasing (see on 1 Chronicles 23:24-27).
To wait upon the service. Literally, "to war the warfare;" the idea of the militia sacra is kept up.