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 sheets for a plating of the altar, since they did present them before the LORD and they are holy; and they shall be for a sign to the sons of Israel.”

as a reminder to the sons of Israel that no layman who is not of the descendants of Aaron should come near to burn incense before the LORD; so that he will not become like Korah and his company—just as the LORD had spoken to him through Moses.