Numbers 4:33-35

New Revised Standard Version, Anglicised

³³ This is the service of the clans of the Merarites, the whole of their service relating to the tent of meeting, under the hand of Ithamar son of Aaron the priest.

Census of the Levites

³⁴ So Moses and Aaron and the leaders of the congregation enrolled the Kohathites, by their clans and their ancestral houses, ³⁵ from thirty years old up to fifty years old, everyone who qualified for work relating to the tent of meeting;