Numbers 16:5, 40

and he spoke to Korah and all his company, saying, “Tomorrow morning the LORD will show who is His, and who is holy, and will bring him near to Himself; even the one whom He will choose, He will bring near to Himself.

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.