Leviticus 10:1; Leviticus 10:2

1 Aaron's sons, Nadab and Abihu, each took his fire pan, put live coals in it, added incense, and presented it to the Lord. But this fire was not holy, because the Lord had not commanded them to present it.

2 Suddenly the Lord sent fire, and it burned them to death there in the presence of the Lord.