Now Nadab and Abihu, the sons of Aaron, each took his censer and put fire in it and laid incense on it and offered unauthorized fire before the LORD, which he had not commanded them.
▸Nadab and Abihu were Aaron's two eldest sons who had just been ordained.
Nadab and Abihu were Aaron's two eldest sons who had just been ordained. 'Unauthorized fire (esh zarah)' means they used fire not commanded by God—fire not taken from the holy fire of the altar. This was not a simple mistake but intentional disobedience that disregarded God's command.