* from twenty.
   In ch. 4:3, the Levites are appointed to the service of the
   tabernacle at the age of 30; years; and in 1; Ch 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 ch. 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.

  4:3,23  1Ch 23:3,24-27  28:12,13 
 * wait upon.  Heb. war the warfare of, etc.
  1Co 9:7  2Co 10:4  1Ti 1:18  6:12  2Ti 2:3-5