C. F. Keil and Franz Delitzsch on Numbers 4:17-18

Num 4:17-18

In order to prevent as far as possible any calamity from befalling the Levites while carrying the most holy things, the priests are again urged by the command of God to do what has already been described in detail in Num 4:5-15, lest through any carelessness on their part they should cut off the tribe of the families of the Kohathites, i.e., should cause their destruction; viz., if they should approach the holy things before they had been wrapped up by Aaron and his sons in the manner prescribed and handed over to them to carry. If the Kohathites should come for only a single moment to look at the holy things, they would die. אל־תּכריתוּ, “cut ye not off,” i.e., “take care that the Kohathites are not cut off through your mistake and negligence” (Ros.). “The tribe of the families of the Kohathites:” shebet, the tribe, is not used here, as it frequently is, in its derivative sense of tribe (Tribus), but in the original literal sense of stirps.