Numbers 4:30 in the King James Version
From thirty years old and upward even unto fifty years old shalt thou number them, every one that entereth into the service, to do the work of the tabernacle of the congregation.
Context
29 “As for the sons of Merari, you shall count them by their families, by their fathers’ houses;
30 you shall count them from thirty years old and upward even to fifty years old—everyone who enters on the service, to do the work of the Tent of Meeting.
31 This is the duty of their burden, according to all their service in the Tent of Meeting: the tabernacle’s boards, its bars, its pillars, its sockets,