And there went out fire from the LORD, and devoured them, and they died before the LORD.

Wesley's Notes

10:2 From the Lord - From heaven, or rather from the sanctuary. Devoured them - Destroyed their lives; for their bodies and garments were not consumed. Thus the sword is said to devour, 2Sam 2:26. Thus lightning many times kill persons, without any hurt to their garments.

Jamieson-Fausset-Brown Bible Commentary

2. there went out fire from the Lord, and devoured them-rather, "killed them"; for it appears (Le 10:5) that neither their bodies nor their robes were consumed. The expression, "from the Lord," indicates that this fire issued from the most holy place. In the destruction of these two young priests by the infliction of an awful judgment, the wisdom of God observed the same course, in repressing the first instance of contempt for sacred things, as he did at the commencement of the Christian dispensation (Ac 5:1-11).

Matthew Henry's Concise Commentary

10:1,2 Next to Moses and Aaron, none were more likely to be honourable in Israel than Nadab and Abihu. There is reason to think that they were puffed up with pride, and that they were heated with wine. While the people were prostrate before the Lord, adoring his presence and glory, they rushed into the tabernacle to burn incense, though not at the appointed time; both together, instead of one alone, and with fire not taken from the altar. If it had been done through ignorance, they had been allowed to bring a sin-offering. But the soul that doeth presumptuously, and in contempt of God's majesty and justice, that soul shall be cut off. The wages of sin is death. They died in the very act of their sin. The sin and punishment of these priests showed the imperfection of that priesthood from the very beginning, and that it could not shelter any from the fire of God's wrath, otherwise than as it was typical of Christ's priesthood.