Numbers 4:28-30 New English Translation (NET)

28. This is the service of the families of the Gershonites concerning the tent of meeting. Their responsibilities will be under the authority of Ithamar son of Aaron the priest.

29. “As for the sons of Merari, you are to number them by their families and by their clans.

30. You must number them from thirty years old and upward to fifty years old, all who enter the company to do the work of the tent of meeting.

Numbers 4