Numbers 4:1-4

1 AND the Lord spake unto Moses and unto Aaron, saying, 2 Take the sum of the sons of Kohath from among the sons of Levi, after their families, by the house of their fathers, 3 From thirty years old and upward even until fifty years old, all that enter into the host, to do the work in the tabernacle of the congregation. 4 This shall be the service of the sons of Kohath in the tabernacle of the congregation, about the most holy things: