Numbers 4:17

"And Jehovah spake unto Moses and unto Aaron, saying, Cut ye not off the tribe of the families of Kohathites from among the Levites; but thus do unto them, that they may live, and not die, when they approach unto the most holy things: Aaron and his sons shall go in, and appoint them every one to his service and to his burden; but they shall not go in to see the sanctuary even for a moment, lest they die."

The meaning of this somewhat ambiguous passage was given thus by Keil:

"In order to prevent as far as possible any calamity from falling upon the Levites while carrying the most holy things, the priests are again urged by the command of God to do all that has already been prescribed (Numbers 4:5-15), lest through any carelessness on their part they should cut off the tribes of the families of the Kohathites, cause their destruction through their approaching the holy things before they had been properly wrapped by Aaron's sons."[11]