Numbers 4:37

35from thirty years old and upward even to fifty years old, everyone who entered into the service for work in the Tent of Meeting.

36Those who were counted of them by their families were two thousand seven hundred fifty.

37These are those who were counted of the families of the Kohathites, all who served in the Tent of Meeting, whom Moses and Aaron counted according to the commandment of the LORD by Moses.

38Those who were counted of the sons of Gershon, by their families, and by their fathers’ houses,

39from thirty years old and upward even to fifty years old—everyone who entered into the service for work in the Tent of Meeting,