From thirty years old and upward— In chap. Numbers 8:24 the age of twenty-five years is appointed for the admission of the Levites to the service of the tabernacle; agreeably to which the LXX. read twenty-five years here, which reconciles the passages. Some, however, suppose, that though the Levites in general were admitted to wait upon the tabernacle, and to administer to the priests at five and twenty, yet they were not put upon the laborious work of carrying the ark and other sacred things upon their shoulders, for which the selection is made in this place, (see Numbers 4:15.) till they were thirty years of age. Hence, in David's time, when the ark was settled, and consequently the work of the Levites less laborious, they were appointed to enter upon their office at twenty years. See 1 Chronicles 23:27 and 2 Chronicles 31:17.
Related Commentaries of Numbers 4:3
Numbers 4:3
3 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.