TSK · Numbers 1:51

So you are to appoint Aaron and his sons, and they will be responsible for their priesthood, but the unauthorized person who comes near must be put to death.”

The Service of the Kohathites Then the LORD spoke to Moses and Aaron:

but in order that they will live and not die when they approach the most holy things, do this for them: Aaron and his sons will go in and appoint each man to his service and his responsibility.

The Journey From Sinai to Kadesh On the twentieth day of the second month, in the second year, the cloud was taken up from the tabernacle of the testimony.

And the Kohathites set out, carrying the articles for the sanctuary; the tabernacle was to be set up before they arrived.

And the staff of the man whom I choose will blossom; so I will rid myself of the complaints of the Israelites, which they murmur against you.”

But you and your sons with you are responsible for your priestly duties, for everything at the altar and within the curtain. And you must serve. I give you the priesthood as a gift for service, but the unauthorized person who approaches must be put to death.”

But the LORD struck down some of the people of Beth Shemesh because they had looked into the ark of the LORD; he struck down 50,070 of the men. The people grieved because the LORD had struck the people with a hard blow.