Numbers 4:17-20

GOD spoke to Moses and Aaron, “Don’t let the tribal families of the Kohathites be destroyed from among the Levites. Protect them so they will live and not die when they come near the most holy things. To protect them, Aaron and his sons are to precede them into the Sanctuary and assign each man his task and what he is to carry. But the Kohathites themselves must not go in to look at the holy things, not even a glance at them, or they will die.”