Numbers 5:1
Various Laws Expulsion of the Impure The Lord spoke to Moses and said:
At the Lord’s command given through Moses, the census was taken to assign to every man his duty and his task; they were numbered as the Lord had commanded Moses.
all the men between thirty and fifty years of age, able to give military service and to be given tasks of carrying burdens in the Tent of Meeting
This was the number of the Merarites whom Moses and Aaron counted at the Lord’s command through Moses.
of every man between thirty and fifty years of age could give military service and be given tasks in the Tent of Meeting.