Numbers 4:20 WBT

¹⁸  Cut ye not off the tribe of the families of the Kohathites from among the Levites:

¹⁹  But thus do to them, that they may live, and not die, when they approach to 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 to see when the holy things are covered, lest they die.

²¹  And the LORD spoke to Moses, saying,

²²  Take also the sum of the sons of Gershon, throughout the house of their fathers, by their families;