“In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:”
King James Version (KJV)
1:8 Taking vengeance - Does God barely permit this, or (as the Lord once rained brimstone and fire from the Lord out of heaven, #Gen 19:24|) does a fiery stream go forth from him for ever? Who know not God - (The root of all wickedness and misery) who remain in heathen ignorance. And who obey not - This refers chiefly to the Jews, who had heard the gospel.
2Th 1:8 In flaming fire. The flaming fire denotes brightness, glory, purity, and also destruction to adversaries. Dazzling brightness is always associated with his coming. God was revealed at Sinai in flaming fire (Ex 3:2; 19:18). Them that know not God. Know him not because they refuse to know him. See Ro 1:28. And obey not the gospel. This class refuse to accept and obey the gospel. Their day of grace will end with the day of the Lord.