Leviticus 10:1-3

Aaron’s sons Nadab and Abihu took their censers, put fire in them and added incense; and they offered unauthorized fire before the LORD, contrary to his command. So fire came out from the presence of the LORD and consumed them, and they died before the LORD. Moses then said to Aaron, “This is what the LORD spoke of when he said: “ ‘Among those who approach me I will be proved holy; in the sight of all the people I will be honored.’ ” Aaron remained silent.