Numbers 8:23-26 - Retirement Of The Levites
23 And Jehovah spoke to Moses saying, 24 This is that which pertains to the Levites. From twenty-five years old and upward they shall go in to wait upon the service of the tabernacle of the congregation. 25 And from the age of fifty years they shall stop waiting upon the service, and shall serve no more. 26 But they shall minister with their brothers in the tabernacle of the congregation, to keep the charge; only he shall not serve at a service. So you shall do to the Levites as to their duties.