Numbers 4:28-30

Revised Standard Version

²⁸ This is the service of the families of the sons of the Gershonites in the tent of meeting, and their work is to be under the oversight of Ith′amar the son of Aaron the priest.

²⁹ “As for the sons of Merar′i, you shall number them by their families and their fathers’ houses; ³⁰ from thirty years old up to fifty years old, you shall number them, every one that can enter the service, to do the work of the tent of meeting.