Why were Nadab and Abihu killed by God?

"And Nadab and Abihu, the sons of Aaron, took either of them his censer, and put fire therein, and put incense thereon, and offered strange fire before the LORD, which he commanded them not. And there went out fire from the LORD, and devoured them, and they died before the LORD." (Leviticus 10:1–2)


The sin of Nadab and Abihu was offering “strange fire before YHWH, which he commanded them not.” (Lev. 10:1) Strange fire most probably has to do with the kind of “fire” they used. Everything in the Tabernacle was purified with blood because “without blood there is no remission” (Heb. 9:22) and “For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul.” (Leviticus 17:11).

The fire to be used in the censers was supposed to come from the altar of sacrifice. Any other fire was not purified for such a holy purpose and was, therefore, “strange fire.”

“And thou shalt make an altar to burn incense upon: of shittim wood shalt thou make it . . . Ye shall offer no strange incense thereon, nor burnt sacrifice, nor meat offering; neither shall ye pour drink offering thereon. And Aaron shall make an atonement upon the horns of it once in a year with the blood of the sin offering of atonements: once in the year shall he make atonement upon it throughout your generations: it is most holy unto the LORD.” (Exodus 30:1, 9–10)

God describes this in more detail:
“And he shall take a censer full of burning coals of fire from off the altar before the LORD, and his hands full of sweet incense beaten small, and bring it within the vail; and he shall put the incense upon the fire before the LORD, that the cloud of the incense may cover the mercy seat that is upon the testimony, that he die not.” (Lev. 16:12–13).

It is possible that Nadab and Abihu saw how God’s presence filled the place when they offered incense and thought it was their doing. They thought they could conjure up God’s presence in a “carnal” way. Even though they offered that incense “before YHWH” (Lev. 10:1), God was forced to show them He meant what He had declared earlier. There’s only one way to please and follow God: His way. Sincerity is not enough. All branches of Christendom, and all other religions, would do well to learn this lesson.