Numbers 16:5, 40

Then he said to Korah and all his followers: “In the morning the LORD will show who belongs to him and who is holy, and he will have that person come near him. The man he chooses he will cause to come near him.

as the LORD directed him through Moses. This was to remind the Israelites that no one except a descendant of Aaron should come to burn incense before the LORD, or he would become like Korah and his followers.