2 Thessalonians 1:8

Those who know not God are of course not pagans as such but immoral pagans, in the sense of Romans 1:28 f. Those who refuse obedience to the gospel are, as the repetition of the article suggests, a different class of people, perhaps drawn both from Jews and pagans. But as Paul never seems to contemplate the idea of any Jew failing to hear the gospel (cf. Romans 10:16 f.), the description here applies principally to them. ἐν πυρὶ φλογός, one of the most favourite realistic traits of the last judgment, in apocalyptic Judaism (cf. passages in Volz's Jüdische Eschatologie, 285, 286); here it is simply a descriptive touch, which Paul does not pause to elaborate (cf. 1 Corinthians 3:13). The rather “broad and inflated” language (Weizsäcker) of the whole passage is probably due to the subject, more than to Paul's employment of Silvanus, himself a prophet (cf. Acts 15:32 and 1 Thessalonians 2:12-16), as his amanuensis.