Numbers 4:16-20

16“The responsibility of Eleazar, the son of Aaron the priest, is the oil for the light, the fragrant incense, the continual grain offering, and the anointing oil—the responsibility of all the tabernacle and everything that is in it, with the sanctuary and its furnishings.”

17Then the Lord spoke to Moses and Aaron, saying,

18“Do not cut off (eliminate, destroy) the tribe of the families of the Kohathites [who are only Levites and not priests], from among the Levites [by exposing them to the sin of touching the most holy things].

19But deal with them in this way, so that they may live and not die when they approach the most holy things: Aaron and his sons shall go in and assign each of them to his [specific] work and to his load [to be carried on the march].

20But the Kohathites shall not go in to see the holy things, even for an instant, or they will die.”