In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:
In flaming fire - Greek 'In (encompassed with) flame of fire ' B Delta G g Vulgate But 'Aleph (') A f read In flaming fire - Greek, 'In (encompassed with) flame of fire.' B Delta G g, Vulgate. But 'Aleph (') A f read, in fire of flame. This flame of fire accompanied His manifestation in the bush (Exodus 3:2); also His giving of the law at Sinai (Exodus 19:18); also it shall accompany His advent (Daniel 7:9-10; Malachi 4:1), symbolizing His own glory and His consuming vengeance against His foes (Hebrews 10:27; Hebrews 12:29; 2 Peter 3:7; 2 Peter 3:10).
Taking - literally, 'giving' them, as their portion, "vengeance."
Know not God - the Gentiles primarily (Psalms 79:6; Galatians 4:8; 1 Thessalonians 4:5); not those involuntarily, but those willfully not knowing Him, as Pharaoh, who might have known God if he would, but boasted, "I know not the Lord" (Exodus 5:2); and as the Thessalonians' persecutors, who might have known God by the preaching of those whom they persecuted. Also all pagans who sin against whatever knowledge of God they have by conscience and from His visible works (Romans 1:20-21; Romans 2:12; Romans 2:14-16). Secondarily, all who 'profess to know God, but in works deny Him' (Titus 1:16).
Obey not the gospel - primarily the unbelieving Jews (Romans 10:3; Romans 10:16). The distinct article implying two distinct classes, marks that primarily the former clause refers to the pagan; this clause to the Jews. Secondarily, all who obey not the truth (Romans 2:8).
Christ. So 'Aleph (') A G f g, Vulgate. Omitted in B Delta.