2 Thessalonians 1:8

In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:

EXPOSITORY (ENGLISH BIBLE)

Ellicott's Commentary for English Readers

(8) In flaming fire.—Most critics agree to change the punctuation here, by omitting the comma after “angels” and inserting it after “fire.” The flaming fire here is not the instrument of the vengeance—i.e., hell-fire—but the common pictorial attribute of the Divine Presence (Exodus 3:2; Exodus 19:18; Daniel 7:9).

Taking vengeance.—The expression in the original is one which is said to be found nowhere else in Greek literature, save in Ezekiel 25:14 (though in Hebrew there is an almost exact equivalent in Numbers 31:3), so that it is difficult to assign the correct meaning. It certainly does not mean “taking vengeance” in the sense of “taking His revenge,” as though our Lord had conceived a personal grudge and were wreaking it. What it does mean would seem to be “assigning retribution:” appointing, that is, to each man what satisfaction of justice he must make. The very word for “vengeance” can only mean vengeance exacted on some one else’s behalf. (Comp. 1Thessalonians 4:6, and Psalm 79:10.)

On them that know not God.—According to the Greek, the word “them” should be repeated also in the next clause. The effect will then be to mark off the culprits into two classes: “them that know not,” and “them that obey not.” A comparison of Ephesians 4:17-18, 1Thessalonians 4:5, shows that by the first class are meant Gentiles; a comparison of Romans 10:16; Romans 10:21 (and many other passages) will show disobedience to be the characteristic of the Jews. The Greek negative particle here is one which shows that the ignorance of the one set and the disobedience of the other were just the points for which they were to be punished: therefore, of course, only those Gentiles whose ignorance was voluntary, who chose (Romans 1:28) to be Gentiles when they might have been joined to the true God, are objects of wrath. Here, as the context shows, St. Paul is thinking chiefly of those Gentiles and Jews who actually persecuted the truth.

Obey not the gospel.—A noteworthy phrase; see the reference. The gospel, the “glad tidings,” contains not only a statement of facts, but also a call to obey a law which is the outcome of the facts. Even the acceptance of evangelical promises requires a submission. (Comp. Luke 24:47; Acts 11:18; Revelation 22:3.) It is here called specially the gospel “of our Lord Jesus Christ,” because the sin of the Jews (who constitute this class of sinners) consisted precisely in the wilful rejection of Jesus as the Christ.

Matthew Henry's Concise Commentary

1:5-10 Religion, if worth anything, is worth every thing; and those have no religion, or none worth having, or know not how to value it, cannot find their hearts to suffer for it. We cannot by all our sufferings, any more than by our services, merit heaven; but by our patience under sufferings, we are prepared for the promised joy. Nothing more strongly marks a man for eternal ruin, than a spirit of persecution and enmity to the name and people of God. God will trouble those that trouble his people. And there is a rest for the people of God; a rest from sin and sorrow. The certainty of future recompence is proved by the righteousness of God. The thoughts of this should be terrible to wicked men, and support the righteous. Faith, looking to the great day, is enabled partly to understand the book of providence, which appears confused to unbelievers. The Lord Jesus will in that day appear from heaven. He will come in the glory and power of the upper world. His light will be piercing, and his power consuming, to all who in that day shall be found as chaff. This appearance will be terrible to those that know not God, especially to those who rebel against revelation, and obey not the gospel of our Lord Jesus Christ. This is the great crime of multitudes, the gospel is revealed, and they will not believe it; or if they pretend to believe, they will not obey it. Believing the truths of the gospel, is in order to our obeying the precepts of the gospel. Though sinners may be long spared, they will be punished at last. They did sin's work, and must receive sin's wages. Here God punishes sinners by creatures as instruments; but then, it will be destruction from the Almighty; and who knows the power of his anger? It will be a joyful day to some, to the saints, to those who believe and obey the gospel. In that bright and blessed day, Christ Jesus will be glorified and admired by his saints. And Christ will be glorified and admired in them. His grace and power will be shown, when it shall appear what he has purchased for, and wrought in, and bestowed upon those who believe in him. Lord, if the glory put upon thy saints shall be thus admired, how much more shalt thou be admired, as the Bestower of that glory! The glory of thy justice in the damnation of the wicked will be admired, but not as the glory of thy mercy in the salvation of believers. How will this strike the adoring angels with holy admiration, and transport thy admiring saints with eternal rapture! The meanest believer shall enjoy more than the most enlarged heart can imagine while we are here; Christ will be admired in all those that believe, the meanest believer not excepted.

Barnes' Notes on the Bible

In flaming fire - This is a circumstance which is not noticed in the account of his appearing in the parallel place in 1 Thessalonians 4:16. The object of the apostle here seems to be to represent him as coming amidst vivid flashes of lightning. He is commonly described as coming in clouds, and to that common description there is here added the image of incessant lightnings, as if the whole heavens were illuminated with a continued blaze.

Taking vengeance - Margin, "yielding." Greek, "giving. The word "vengeance" is used in the sense of punishment, for there cannot be in God what literally corresponds with the passion of revenge; compare the notes on Romans 12:19.

On them that know not God. - On all who are strangers to him; that is, who are living in pagan darkness, or who, having heard of him, have no practical acquaintance with him.

And that obey not the gospel of our Lord Jesus Christ. - Who do not embrace it, and practice its precepts in their lives; compare the notes on Romans 2:9.

Jamieson-Fausset-Brown Bible Commentary

8. In flaming fire—Greek, "In flame of fire"; or, as other oldest manuscripts read, "in fire of flame." This flame of fire accompanied His manifestation in the bush (Ex 3:2); also His giving of the law at Sinai (Ex 19:18). Also it shall accompany His revelation at His advent (Da 7:9, 10), symbolizing His own bright glory and His consuming vengeance against His foes (Heb 10:27; 12:29; 2Pe 3:7, 10).

taking—literally, "giving" them, as their portion, "vengeance."

know not God—the Gentiles primarily (Ps 79:6; Ga 4:8; 1Th 4:5); not of course those involuntarily not knowing God, but those wilfully not knowing Him, as Pharaoh, who might have known God if he would, but who boasted "I know not the Lord" (Ex 5:2); and as the heathen persecutors who might have known God by the preaching of those whom they persecuted. Secondarily, all who "profess to know God but in works deny Him" (Tit 1:16).

obey not the gospel—primarily the unbelieving Jews (Ro 10:3, 16); secondarily, all who obey not the truth (Ro 2:8).

Christ—omitted by some of the oldest manuscripts, and retained by others.

Matthew Poole's Commentary

But his coming will be upon another account to many others, which is said here to be to take vengeance, for which purpose he is said to be revealed with his mighty angels, or angels of might; and elsewhere, with all his holy angels. They are said to excel in strength, Psalm 103:20, or to be mighty in strength, and have the name of might, Ephesians 1:21. And here called mighty, because as the work Christ comes upon is great and difficult, so he will have instruments sufficient for it, and none shall be able to hinder. And though he hath power himself sufficient, yet the angels must attend him to solemnize this great day, and to be serviceable to him in the work thereof, which, as it will respect the saints in their resurrection from the dead, and their gathering from the four winds, and separating them from the ungodly, as tares from the wheat and sheep from the goats, so the taking vengeance also in this day of the Lord’s wrath, which the apostle, especially, is in these verses speaking of, is the work they shall be employed in. As also in flaming fire, or the fire of flame, a Hebraism. Fire is the most dreadful of all the elements, especially flaming, to denote the great wrath of that day, and its breaking forth, as fire when it flameth. God’s wrath is often expressed in Scripture by fire, Deu 32:22 Psalm 97:3, &c.; Jeremiah 21:12 Hebrews 10:27; and as that which attendeth the great day of Christ, Daniel 7:10 1 Corinthians 3:13 2 Peter 3:7,12. And whether this flaming fire is material, or only metaphorical; if material, whether the present elementary fire, which shall descend, and be joined with that which shall break forth out of the bowels of the earth, as in Noah’s flood the waters were from above and from beneath; or whether it shall be some new created fire, and the action of it natural, or supernatural, I shall leave it to the schoolmen. Yet it is generally conceived it is a material fire; else how can the elements be said to melt with fervent heat, and the world and the works thereof burnt up, as the apostle Peter speaks, 2 Peter 3:10; and parallels it with the deluge in Noah’s time, which was with material water. But yet it is to be a manifestation of the fire of God’s wrath, and an instrument of it also in the destruction of ungodly men, 2 Peter 3:7; for it is said in the text, Christ is revealed in it to take vengeance. Vengeance is an act of justice; it is a retribution of evil for evil, the evil of suffering for the evil done: and God claims it as belonging to himself, Psalm 94:1 Romans 12:19 Hebrews 10:27; and it is mentioned in the parable, Luke 18:7,8, as one great work of Christ, at his coming, to avenge the elect.

On them that know not God; these are the persons upon whom he will execute vengeance: by whom some think are meant the heathen, who had not the gospel. Those that had not the gospel, yet had means to know God, by the light of nature, and the works of creation and providence, which if they did not improve, but remained ignorant of God, will fall under this vengeance. And by knowledge here is not meant so much a speculative as a practical knowledge of God; and so such as do not fear, love, and honour God, may be said not to know him. As the Gentiles, who are said to know God, Romans 1:21, but yet not glorifying him as God, and living in idolatry, are said not to know him, Galatians 4:8 1 Thessalonians 4:5. And as God tells the king of Judah, that to do justice and judgment is to know him, Jeremiah 22:16. And Eli’s sons, though priests, yet are said not to know the Lord, 1 Samuel 2:12.

And that obey not the gospel; which may be taken in conjunction with the former words, and then such as obey not the gospel are the same with them that know not God. As God is not known aright but by the gospel, so they only know God aright by the gospel who obey it. Some are ignorant and know not God, though they live under the gospel. Or, such as have knowledge, yet are not obedient. Knowledge and obedience ought to go together. And this obedience is called the obeying of the gospel. The gospel hath not only promises to be believed, but precepts to be obeyed. Yea, faith itself may fall under its precepts, and then those that believe not the gospel do not obey it: as the same word in the Greek signifies to believe and obey. And as the gospel hath some peculiar precepts and institutions, so all the commands of the moral law are comprehended in it; and the equitable part of the judicial law, yea, and the ceremonial law also, where that which is moral is figured by it; and so far as the gospel commands, men ought to obey; and disobedience appears to be a great evil, when it will expose men to this great vengeance. So Romans 2:8,9: To them that do not obey the truth, indignation and wrath, tribulation and anguish, & c. Not to obey the law of nature, exposed the heathen to God’s wrath, Romans 1:18; and to disobey the law of Moses, the Jew, Romans 2:2 Hebrews 2:3 10:28 Hebrews 12:25; much more not to obey the gospel. Christ is said here especially to take vengeance of such at his coming. Gospel sins are most heinous and most provoking, and will be most severely punished.

Gill's Exposition of the Entire Bible

In flaming fire,.... Which may either refer to Christ, who will be revealed from heaven in such a manner; and whose coming will be as the lightning, not only sudden, but glorious, illustrious, and visible; he will be seen and easily discerned; there will be such a light and flaming fire about him, which, as it will serve to make him visible, will greatly add to the majesty of his appearance, and strike terror to his enemies, and burn them up round about; see Daniel 7:7 or else it may refer to the angels, who shall descend in fiery forms, which is agreeably to their nature, Psalm 104:4 and so they appeared in the forms of horses of fire, and chariots of fire, when Elijah was carried up to heaven. And it is a tradition of the Jews (z), that the angel Gabriel descended , "in a flame of fire", to burn Moses, as he was in the inn, when upon his journey from Midian to Egypt: or this clause may be read in construction with the following, as it is in the Vulgate Latin and Syriac versions, "in flaming fire taking vengeance"; and so expresses the manner in which vengeance will be taken on the wicked by Christ, the Judge of all, to whom it belongs: and the punishment of ungodly men is often signified by fire, and flames of fire, by the fire of hell, and a lake which burns with fire and brimstone, by a furnace of fire, everlasting fire, and fire that cannot be quenched, to set forth the endless torture and inconceivable misery of the damned; and it may be, some regard is had to the general conflagration, which will be at the coming of Christ, when the heavens, being on fire, shall be dissolved, the elements shall melt with fervent heat, and the earth, and all that is in it, shall be burnt up, when the bodies of the wicked, then living, will be consumed in flames of fire, and their souls feel the wrath of the Almighty. The persons who will then be punished, and on whom vengeance will be taken, are described as follows,

on them that know not God; which is a periphrasis, or common character of the Gentiles, 1 Thessalonians 4:5 who know not the one, true, and living God; or know him not so as to glorify him as God, and be thankful to him for the mercies they receive from him, and still less know him in Christ Jesus; which ignorance of theirs is not without sin, nor will it excuse from punishment; for though vengeance will not be taken on them, because they have not a spiritual saving knowledge of God, in the Mediator Jesus Christ, who never was revealed to them; yet forasmuch as they had the light and law of nature, by which the being of God, and the invisible perfections of his nature might be seen and understood, and much of his will, with respect to moral good and evil, be known, against both which they have rebelled, and having sinned, will perish without law: though it may also include all such persons, who having been favoured with an external revelation, have professed to know God, and yet in works have denied him:

and that obey not the Gospel of the Lord Jesus Christ; of which Christ is the author, was the preacher, and is the sum and substance; which is good news and glad tidings of the grace of, God, of peace, pardon, righteousness, life, and salvation by Christ; which may be said to be obeyed, when it is received and embraced by faith, with and from the heart, and confession is made of it with the mouth, and the ordinances of it are submitted to; and which is called the obedience of faith, because faith without obedience is not right, and obedience without faith is of no avail: but all that hear the Gospel do not obey it; there are some that disbelieve and reject the doctrines and ordinances of it, and others that, do profess it, and do not yield a cordial and cheerful obedience to it; both may be reckoned among the disobeyers of it: and though the unbelieving Jews may be chiefly designed here, yet deists of every age and place, where the Gospel revelation has come, and carnal professors, and profane despisers everywhere, may be included; whose condemnation will be aggravated by the external light which has shone around them, and they have hated; the severest punishment will be inflicted on them; it will be more tolerable for Tyre and Sidon, Sodom and Gomorrah, than for such persons; see 1 Peter 4:17.

(z) Zohar in Gen. fol. 63. 2.

Geneva Study Bible

In flaming fire taking vengeance on them {6} that know not God, and that obey not the gospel of our Lord Jesus Christ:

(6) There is no knowledge of God to salvation, without the Gospel of Christ.

EXEGETICAL (ORIGINAL LANGUAGES)

Meyer's NT Commentary

2 Thessalonians 1:8. Ἐν φλογί πυρός] is not, as Estius, Cornelius a Lapide, Seb. Schmid, Harduin, Moldenhauer, Macknight, Hilgenfeld (Zeitsch. f. wissensch. Theol. 1862, Part 3, p. 245), Hofmann, and others[38] assume, a statement declaring the instrument of ΔΙΔΌΝΤΟς ἘΚΔΊΚΗΣΙΝ, but is a further specification of the mode of ἈΠΟΚΑΛΎΨΕΙ, 2 Thessalonians 1:7 : in flaming fire (בְּלַהַב אֵשׁ Isaiah 29:6; Isaiah 30:30, etc.). In the O. T. God is described as appearing in flames of fire, and especially His coming to judgment is described as a coming in fire; comp. Exodus 3:2 ff; Exodus 19:18; Daniel 7:9-10, etc. What is there asserted of God is here transferred to Christ. (Comp. also 1 Corinthians 3:13, where of the day of Christ, i.e. of His advent, it is said: ἘΝ ΠΥΡῚ ἈΠΟΚΑΛΎΠΤΕΤΑΙ.) The additional clause accordingly serves for a further exaltation of the majesty and glory in which Christ will return. More special statements, that Paul thought on thunder and lightning (Zachariae, Koppe, Bolten), on a fire consuming the ungodly, or the world, or both together (Zwingli, Hemming, Aretius, Cornelius a Lapide, Fromond., Sebastian Schmid, and others), are to be discarded, from want of data to decide on.

διδόντος] is joined, not to πυρός, but to τοῦ κυρίου Ἰησοῦ, 2 Thessalonians 1:7. The formula διδόναι ἐκδίκησίν τινι, to impart vengeance, that is, punishment, to any one, is only found here in the N. T. But comp. the LXX. Ezekiel 25:14; Numbers 31:3 (נָתַן נְקָמָה). Paul does not mention only one class of persons who are to be punished (Calvin, Hemming, Turretin, Pelt, Schott, de Wette, Riggenbach), but two classes of persons. This is required by the article repeated before μὴ ὑπακούουσιν. These were the two classes of persons from whom the church of Thessalonica had to suffer persecution

Gentiles and Jews. By ΤΟῖς ΜῊ ΕἸΔΌΣΙΝ ΘΕΌΝ Paul means the former, and by ΤΟῖς ΜῊ ὙΠΑΚΟΎΟΥΣΙΝ Τῷ ΕὐΑΓΓ. Κ.Τ.Λ. the latter, so that the general ΤΟῖς ΘΛΊΒΟΥΣΙΝ ὙΜᾶς, 2 Thessalonians 1:6, is now specialized. The correctness of this interpretation is further evident from the fact that elsewhere ΜῊ ΕἸΔΌΤΕς ΘΕΌΝ is with Paul a characteristic designation of the Gentiles (1 Thessalonians 4:5; Galatians 4:8; comp. Romans 1:28; Ephesians 2:12); whereas the characteristic of the theocratic nation of the Jews, as shown by experience, was disobedience to God and His plan of salvation; comp. Romans 10:3; Romans 10:16; Romans 10:21, etc. This reference to Gentiles and Jews is already found in Ambrosiaster, Grotius, Quistorp, Benson, Bengel, Koppe, Baumgarten-Crusius; and also recently, in Alford, Ewald, and Bisping. On the other hand, Harduin and Hofmann interpret the first clause of Gentiles, and the second of Jews and Gentiles; Schrader, the first of Gentiles, and the second of Christians; Aretius, the first of “manifesti Christi hostes, sive Judaei sint sive ethnici,” and the second of “pestes in sinu ecclesiae latitantes.” But with the first view the division, which the article repeated requires, becomes illusory; and the context decides against the last two views. For when, as here, Christians are comforted on account of the afflictions which they suffer from those who are not Christians by an intimation of a future retribution, the discourse cannot possibly have reference to a punishment which is impending on Christians.

τοῦ κυρίου ἡμῶν Ἰησοῦ] a repetition of the subject already contained in διδόντος in a fuller form, on account of the preceding Θεόν.

[38] Thus also Theodoret must have united the words. For although he does not clearly express himself concerning this union, yet he finds in φλογὶ πυρός expressed: τῆς τιμωρίας τὸ εἶδος, and adds: φλογὶ γὰρ πυρὸς παραδίδονται.

Expositor's Greek Testament

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.

Cambridge Bible for Schools and Colleges

8. in flaming fire] Lit., fire of flame; or, in other copies, flame of fire. “Fire” is a symbol of Divine anger and majesty, in Scripture; and “flame” is fire in motion, leaping and blazing out. According to 2 Peter 3:7; 2 Peter 3:10, fire will be the means of destruction for the visible world at the Day of the Lord; while in Hebrews 1:7, quoted from Psalms 104, this element is represented as a form of angelic manifestation (see last note). In 1 Corinthians 3:13-15 fire is itself made the means of judgement.

The comma parting this clause from 2 Thessalonians 1:7 in the A.V. must be struck out. The “flaming fire” is the element “in” which the Lord Jesus is “revealed” not the means by which He “takes vengeance” on the wicked. It is His awful robe of glory. The words which follow show why He must appear hi majesty so dreadful:

taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ] Better, rendering vengeance to them (R. V.). We must dissociate from “vengeance” all notions of vindictiveness and passion; it is the inflicting of full justice on the criminal—nothing more, nothing less. In this sense it is written, “Vengeance belongeth unto Me; I will repay, saith the Lord” (Deuteronomy 32:35; Romans 12:19; Hebrews 10:30). The wronged are forbidden to avenge themselves, just because this is God’s prerogative. Now “the Father hath committed all judgement to the Son” (John 5:22)—this, therefore, with the rest.

The R. V. properly distinguishes the two classes here marked out for retribution. Those who know not God belong to the heathen; on this expression comp. note to 1 Thessalonians 4:5. In Romans 1:18-25, speaking of the heathenism of his own day and of the course and working of Gentile idolatry, the Apostle declares that this ignorance of God was wilful, that idolatry was the outcome of ungodliness, and that its wickedness was shown by the horrible depravity of morals it produced. It was therefore culpable in the highest degree and merited vengeance, being the ignorance of men who “did not think God worth having in their knowledge” (Romans 1:28). Such is the sentence that St Paul pronounces on the Paganism of his time, in view of its general character and fruits. By no means does he suppose that this “vengeance” will fall on all idolaters at the Last Day, and for the mere fact of “not knowing God” as Christians do. He speaks otherwise in Romans 2:14. Countless millions of heathen have had no such knowledge of God brought to them. Each will be judged according to his personal responsibility and share in the common offence. God “leaves Himself not without witness to any” (Acts 14:17; John 1:9); and by the measure of light and opportunity vouchsafed to him will the conduct of every man be weighed and estimated. The Apostle is thinking of the Gentile persecutors at Thessalonica (2 Thessalonians 1:6), who refused the knowledge of God and showed their hatred to Him by their hatred toward His children (comp. John 15:24; 1 John 3:13).

Those who obey not the gospel are all, whether Jews or Gentiles, to whose knowledge God’s good news of Christ is brought, and who reject the message. Obedience is practical faith, the submission of heart and life to the demands of Christ. This is what such men refuse; they will not say, “Jesus is Lord” (1 Corinthians 12:3; Php 2:10). And the wilful rejecters of Christ became furious persecutors.

St Paul’s warning echoes that of Christ concerning all who are brought face to face with His Gospel: “He that disbelieveth shall be condemned” (Mark 16:16). This condemnation takes effect at once, and operates in the present life; it has the certainty of a moral law: “He that believeth not is condemned already. And this is the condemnation, that light is come into the world, and men loved darkness rather than light” (John 3:18-19). This sentence the Lord Jesus pronounces now on those who, with His light shining upon them, refuse Him the obedience of faith. The Judgement of the Last Day will be the consummation of this present, actual judgement.

Read our Lord Jesus, for our Lord Jesus Christ.

Bengel's Gnomen

2 Thessalonians 1:8. Ἐν πυρὶ φλογὸς) Others read ἐν φλογὶ πυρὸς.[1] The same variety occurs, Acts 7:30 : ἐν φλογὶ πυρὸς, LXX., Isaiah 66:15.—ΤΟῖς ΜῊ ΕἸΔΌΔΙ ΘΕῸΝ) to those who are living in heathen ignorance of God, 1 Thessalonians 4:5; Psalm 79:6. So Job 18:21, לא ידע אל, ΤῶΝ ΜῊ ΕἸΔΌΤΩΝ ΤῸΝ ΚΎΡΙΟΝ, of those[2] who know not the Lord.—μὴ ὑπακούουσι, who do not obey) chiefly by the Jews, to whom the Gospel concerning Christ[3] had been preached.

[1] Lachm. reads ἐν φλογὶ πυρὸς with BD(Δ)Gg Vulg., Iren. 273, 265. Tisch. reads ἐν πυρὶ φλογὸς with Af and Rec. Text.—ED.

[2] The Hebrew is sing., of him that knoweth not God.—TR.

[3] It is considered, however, by the margin of the 2d ED., that the name of Christ should rather be omitted in this verse, and therefore the Germ. Vers. has rejected it.—E. B.

BD(Δ) omit Χριστοῦ, and so Tisch. But AGfg Vulg., Iren. 265, and Rec. Text, support it. Lachm. therefore retains it, but in brackets.—ED.

Pulpit Commentary

Verse 8. - In flaming fire; not the instrument of punishment - "in flaming fire taking vengeance;" but a further description of the glory of Christ's appearance - "revealed in flaming fire." In the Old Testament God is represented as appearing in flaming fire, as when he manifested himself to Moses in the burning bush (Exodus 3:2; Acts 7:30); and especially his coming to judgment is represented as coming in fire (Psalm 97:3). What is there asserted of God is here referred to Christ (comp. Revelation 19:22). There is also a probable reference to the Shechinah or cloud of glory in which Christ will appear for judgment trey. 1:7). Some also suppose a reference to the fire of the universal conflagration which shall usher in the last day (2 Peter 3:10), and others to the fire which shall consume the ungodly, but it is best to restrict the expression to the glory of Christ's manifestation. Taking vengeance; literally, giving; that is, awarding or allotting vengeance, representing the act, not of a conqueror or of an avenger, but of a righteous Judge. On them that know not God - the unbelieving Gentiles - and that; or rather, on them that; a second class being here denoted. Obey not the gospel of our Lord Jests Christ; namely, the unbelieving Jews. The ignorance of the one and the disobedience of the other were the causes of their punishment. 2 Thessalonians 1:8

Vincent's Word Studies

In flaming fire (ἐν πυρὶ φλογός)

Lit. in a fire of flame. Comp. 1 Corinthians 1:13; 2 Peter 3:7.

Taking vengeance (διδόντος ἐκδίκησιν)

Lit. giving or rendering. Vengeance is an unfortunate rendering, as implying, in popular usage, personal vindictiveness. See on 2 Corinthians 7:11. It is the full awarding of justice to all parties.

On them that know not God - obey not the gospel (τοῖς μὴ εἰδόσι θεὸν - τοῖς μὴ ὑπακούουσιν τῷ εὐγγελίῳ)

To know God is to know him as the one, true God as distinguished from false gods; to know his will, his holiness, his hatred of sin, and his saving intent toward mankind. Two words are used of such knowledge, εἰδέναι and γινώσκειν. Both are applied to the heathen and to Christians, and both are used of the Jews' knowledge of God. Ἑιδέναι, of heathen, Galatians 4:8; 1 Thessalonians 4:5; 2 Thessalonians 1:8. Γινώσκειν of heathen, Romans 1:21; 1 Corinthians 1:21. Ἑιδέναι, of Christ and Christians, John 7:29, John 8:19, John 8:55; John 14:7. Γινώσκειν of Christ and Christians, Galatians 4:9; 1 John 2:13, 1 John 2:14; 1 John 4:6, 1 John 4:7, 1 John 4:8; John 10:15; John 17:3. In John, γινώσκειν of Jews who do not know the Father, John 16:3; John 8:55 : εἰδέναι, John 7:28; John 8:19; John 15:21. The two are combined, John 1:26; John 7:27; John 8:55; 2 Corinthians 5:16. A distinction is asserted between γινώσκειν as knowledge grounded in personal experience, apprehension of external impressions - and εἰδέμαι purely mental perception in contrast with conjecture or knowledge derived from others. There are doubtless passages which bear out this distinction (see on John 2:24), but it is impossible to carry it rigidly through the N.T. In the two classes, - those who know not God and those who obey not the gospel, - it is not probable that Paul has in mind a distinction between Jews and Gentiles. The Jews were not ignorant of God, yet they are described by John as not knowing him. The Gentiles are described by Paul as knowing God, but as refusing to glorify him as God (Romans 1:21). Paul rather describes here the subjects of God's judgment as one class, but under different aspects.