Numbers 4:18

4:18 “Do not allow the tribe of the families of the Kohathites to be cut off ¹  from among the Levites;

Numbers 32:28

32:28 So Moses gave orders about them to Eleazar the priest, to Joshua son of Nun, and to the heads of the families of the Israelite tribes.

[4:18]  ¹ sn The verb is simply the Qal, “do not cut off.” The context calls for a permissive nuance – “do not let them be cut off.” It was a difficult task to be handling the holy things correctly; Moses and Aaron were to see to it that they did it right and did not handle the objects, that is, Moses and Aaron were to safeguard their lives by making certain that proper procedures were followed.