just as the LORD commanded him through Moses. This was to be a reminder to the Israelites that no outsider who is not a descendant of Aaron should approach to offer incense before the LORD, lest he become like Korah and his followers.
Jewish Publication Society of America Version (JPS1917) - Numbers 16:40 >(17-5) to be a memorial unto the children of Israel, to the end that no common man, that is not of the seed of Aaron, draw near to burn incense before the LORD; that he fare not as Korah, and as his company; as the LORD spoke unto him by the hand of Moses.