Numbers 8:23-26 - Retirement Of The Levites
23 And Jehovah will speak to Moses, saying, 24 This is that to the Levites: from the son of five and twenty years and above, and he came in to war the warfare in serving the tent of appointment 25 And from the son of fifty years, he shall turn back from the warfare of the service, and shall serve no more. 26 And he served with his brethren in the tent of appointment, to watch the watches, and he shall work no work. Thus shalt thou do to the Levites in their watches.