From thirty years old and upward even until fifty years old, all that enter into the host, to do the work in the tabernacle of the congregation. (Numbers 4:3)
These men would be in the prime of their physical life, and well fitted for the work of carrying the tabernacle and its equipment. In ch. 8:23-26 the age is given as between 25 and 50 years. Later writers record a further adjustment, attributed to David, beginning the service at 20 years of age (1 Chron. 23:24, 27; 2 Chron. 31:17; Ezra 3:8). An Apocryphal writer also mentions this (1 Esdras 5:58). The first injunction, giving the beginning age as 30 years, may have been a temporary measure. Thirty years marked the age at which a Jew was considered mature and ready to assume all the responsibilities of his rights and privileges (cf. Luke 3:23). Beyond the age of 50 a Levite was not bound to do service, but merely to assist in the tabernacle according to his ability (Num. 8:25, 26).
The host.
From a Hebrew word used for an army in ordered array, and so used again and again in the Scriptures. It may also be translated “warfare,” referring to the fighting service in which the recruits and their officers had to engage. In this verse it has reference to the sacred duties of a soldier of God. This is the Christian of today understands as the service of a soldier of the cross.