Numbers 4:28-30

Amplified Bible, Classic Edition

²⁸ This is the service of the families of the sons of Gershon in the Tent of Meeting; and their work shall be under the direction of Ithamar son of Aaron, the [high] priest.

²⁹ As for the sons of Merari, 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, everyone who enters the service to do the work of the Tent of Meeting.