In Leviticus 10, we learn about the death of Nadab and Abihu, Aaron's sons who didn't follow the commands of the Lord. They offered unauthorized fire before the Lord, and the fire came out from the presence of the Lord and consumed them. "All the house of Israel may mourn for those the Lord destroyed by fire." The Lord said to Aaron, "You must distinguish between the holy and the common, between the unclean and the clean, and you must teach the Israelites all the decrees the Lord has given them through Moses."