Numbers 8:20-26 - The Levites Are Dedicated To The Lord
20 Thus did Moses, and Aaron, and all the congregation of the sons of Israel, to the Levites. According to all that LORD commanded Moses concerning the Levites, so the sons of Israel did to them. 21 And the Levites purified themselves from sin, and they washed their clothes. And Aaron offered them for a wave-offering before LORD, and Aaron made atonement for them to cleanse them. 22 And after that the Levites went in to do their service in the tent of meeting before Aaron, and before his sons. As LORD had commanded Moses concerning the Levites, so they did to them.
23 And LORD spoke to Moses, saying, 24 This is that which belongs to the Levites: From twenty-five years old and upward they shall go in to wait upon the service in the work of the tent of meeting. 25 And from the age of fifty years they shall cease waiting upon the work, and shall serve no more, 26 but shall minister with their brothers in the tent of meeting, to keep the charge, and shall do no service. Thus shall thou do to the Levites concerning their charges.