"As for the sons of Merari, you shall number them by their families and by their fathers' house.
Numbers 4:29
Surrounding context
4:28 This is the service of the families of the sons of Gershon in the tabernacle of meeting. And their duties shall be under the authority of Ithamar the son of Aaron the priest.
4:29 "As for the sons of Merari, you shall number them by their families and by their fathers' house.
4:30 From thirty years old and above, even to fifty years old, you shall number them, everyone who enters the service to do the work of the tabernacle of meeting.