Numbers 16:40
40 to be a reminder to the people of Israel, so ythat no outsider, who is not of the descendants of Aaron, should draw near to burn incense before the Lord, lest he become like Korah and his company—as the Lord said to him through Moses.
Numbers 18:7
7 And cyou and your sons with you shall guard your priesthood for all that concerns the altar and dthat is within the veil; and you shall serve. I give your priesthood as a gift,1 and eany outsider who comes near shall be put to death.”