John Calvin Commentary Numbers 16:40

"to be a memorial unto the children of Israel, to the end that no stranger, that is not of the seed of Aaron, come near to burn incense before Jehovah; that he be not as Korah, and as his company: as Jehovah spake unto him by Moses." — Numbers 16:40 (ASV)

To be a memorial to the children of Israel. This passage again confirms what I have just said: God’s judgments, which should remain in full remembrance in every age, quickly escape and are blotted out from people's minds unless they are provided with certain aids to meditate on them. This, however, does not happen so much from ignorance as neglect. Therefore, we should be more attentive to the aids to memory that keep us in the path of duty.