Numbers 16:38, 40

As for the censers of these men who have sinned at the cost of their lives, let them be made into hammered plates as a covering for the altar, for they offered them before the LORD, and they became holy. Thus they shall be a sign to the people of Israel.”

to be a reminder to the people of Israel, so that 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.