and those who were listed by genealogy of the priests by their fathers’ houses, and the Levites from twenty years old and upward, in their offices by their divisions;
These are those who were counted of the families of the sons of Merari, whom Moses and Aaron counted according to the commandment of the LORD by Moses.
from thirty years old and upward even to fifty years old, everyone who entered in to do the work of service and the work of bearing burdens in the Tent of Meeting,