Numbers 4:35 in the King James Version
From thirty years old and upward even unto fifty years old, every one that entereth into the service, for the work in the tabernacle of the congregation:
Context
34 Moses and Aaron and the princes of the congregation counted the sons of the Kohathites by their families, and by their fathers’ houses,
35 from thirty years old and upward even to fifty years old, everyone who entered into the service for work in the Tent of Meeting.
36 Those who were counted of them by their families were two thousand seven hundred fifty.