Numbers 4:21 DBY

¹⁹  but this shall ye do unto them, that they may live, and not die, when they draw near unto the most holy things: Aaron and his sons shall go in, and appoint them every one to his service and to his burden;

²⁰  but they shall not go in and see for a moment the holy things, lest they die.

²¹  And Jehovah spoke to Moses, saying,

²²  Take also the sum of the sons of Gershon, according to their fathers' houses, after their families.

²³  From thirty years old and upward to fifty years old shalt thou number them; every one that cometh to labour in the work, to perform the service in the tent of meeting.