Then Nadab and Abihu, the sons of Aaron, each took his censer and put fire in it, put incense on it, and offered foreign fire before the Lord, which He had not commanded them. 2 So fire went out from the Lord and devoured them, and they died before the Lord. 3 And Moses said to Aaron, “This is what the Lord spoke, saying: ‘By those who come near Me, I must be regarded as holy; And before all the people, I must be glorified.’” So Aaron held his peace.
This is not only a personal tragedy, but a national one as well. For 25 chapters--the last 16 of Exodus and the first 9 of Leviticus--the Israelites are dedicated to one purpose: constructing and consecrating the Tabernacle and its vessels, including the human ones, Aaron and his four sons. Now, the elder two--already designated for greatness at Sinai (Exod. 24:1-9)--are dead, precisely at the height of the celebration, the eighth (shemini) day, following a week-long initiation process.
So what did they do wrong? The Baal Haturim, famous for his love of mnemonics and gematria, here hews closely to the simple meaning of the words.
"Which He had not commanded them"--now, we cannot say that he neither commanded them to do so nor commanded them not to do so! Rather, it means "which he commanded them not to." The same is true of "or any of the host of heaven, which I have not commanded" (Deut. 17:3) [that God commanded not to worship the stars].
What law did they violate? Apparently, Baal Haturim alludes to Exod. 30:9: "You shall not offer foreign incense on it." But if the prohibition is foreign incense, why speak of "foreign fire," both here and in Numbers 3:4?The fact is that fire is a leitmotif in Shemini, appearing no less than--what else?--eight times in the story of the eighth day. At first, the fire is outside the camp, for the incineration of a special type of sin-offering. At the completion of the ceremony, Aaron blesses the people and a fire comes down from heaven to light up the altar, at the center of the camp. By then kindling their own fire, Nadab and Abihu defile the Tabernacle and defy God, for which they end up paying the ultimate price, as a divine fire comes forth to devour them. To set matters straight, Moshe stresses three times that the survivors, Aaron, Eleazar and Ithamar, must eat their portions from "the fires of the Lord." Procedure must be followed, even in their bereavement.
All of this seems esoteric to the modern reader. Divine fire, profane fire--what does it all mean? However, the power of our fire is far from a moot point. The idioms are the same in English and Hebrew: opening fire, ceasefire, under fire. When we hold our fire and when we fire away are questions of morality. The stakes are so high that we as a society must be exacting in determining when such fire is justified and when it is not. Nadab and Abihu, after all, were righteous men, destined for positions of prominence, but their momentary error in judgment doomed them. God knew what was in their heart; all we have is a system of laws to try to uncover the truth of the matter. In the meantime, we must reaffirm our commitment to never profane the awesome power of our fire.