from twenty: In Numbers 4:3, the Levites are appointed to the service of the tabernacle at the age of 30 years; and in 1 Chronicles 23:24, they are ordered to commence their work at 20 years of age. In order to reconcile this apparent discrepancy, it is to be observed:
1. At the time of which Moses speaks in Numbers 4:3, the Levitical service was exceedingly severe, and consequently required full grown, robust men, to perform it; the age of 30 was therefore appointed as the period for commencing this service, the weightier part of which was probably there intended.
2. In this place God seems to speak of the service in a general way. Hence the age of 25 is fixed.
3. In David's time, and afterwards, in the fixed tabernacle and temple, the laboriousness of the service no longer existed, and hence 20 years was the age appointed. Numbers 4:3, Numbers 4:23; 1 Chronicles 23:3, 1 Chronicles 23:24-27, 1 Chronicles 28:12-13
wait upon: Heb. war the warfare of, etc. 1 Corinthians 9:7; 2 Corinthians 10:4; 1 Timothy 1:18, 1 Timothy 6:12; 2 Timothy 2:3-5