Numbers 8:22-26

Webster_Strongs(i)
  22 H310 And after H935 [H8804] that went H3881 the Levites H5647 [H8800] in to perform H5656 their service H168 in the tabernacle H4150 of the congregation H6440 before H175 Aaron H6440 , and before H1121 his sons H3068 : as the LORD H6680 [H8765] had commanded H4872 Moses H3881 concerning the Levites H6213 [H8804] , so did they to them.
  23 H3068 And the LORD H1696 [H8762] spoke H4872 to Moses H559 [H8800] , saying,
  24 H3881 This is it that which pertaineth to the Levites H6242 : from twenty H2568 and five H8141 years H1121 old H4605 and upward H935 [H8799] they shall go in H6633 H6635 [H8800] to wait H5656 upon the service H168 of the tabernacle H4150 of the congregation:
  25 H1121 And from the age H2572 of fifty H8141 years H7725 [H8799] they shall cease H6635 waiting H5656 upon the service H5647 [H8799] of it, and shall serve no more:
  26 H8334 [H8765] But shall minister H251 with their brethren H168 in the tabernacle H4150 of the congregation H8104 [H8800] , to keep H4931 the charge H5647 [H8799] , and shall do H5656 no service H6213 [H8799] . Thus shalt thou do H3881 to the Levites H4931 concerning their charge.