Numbers 4:21-23

American Standard Version

²¹ And Jehovah spake unto Moses, saying, ²² Take the sum of the sons of Gershon also, by their fathers’ houses, by their families; ²³ from thirty years old and upward until fifty years old shalt thou number them; all that enter in to ^[a]wait upon the service, to do the work in the tent of meeting.