Leviticus 10:1-3

Now Nadab and Abihu, the sons of Aaron, took their respective firepans, and after putting fire in them, placed incense on it and offered strange fire before the LORD, which He had not commanded them. And fire came out from the presence of the LORD and consumed them, and they died before the LORD. Then Moses said to Aaron, “It is what the LORD spoke, saying, ‘By those who come near Me I will be treated as holy, And before all the people I will be honored.’ ” So Aaron, therefore, kept silent.