Numbers 8:24-26

Young's Literal Translation

²⁴ `This [is] that which [is] the Levites': from a son of five and twenty years and upward he doth go in to serve the host in the service of the tent of meeting,

²⁵ and from a son of fifty years he doth return from the host of the service, and doth not serve any more,

²⁶ and he hath ministered with his brethren in the tent of meeting, to keep the charge, and doth not do service; thus thou dost to the Levites concerning their charge.'