For Jehovah will judge in fire. Here he brings forward nothing new, but merely confirms the former statement, and shews that this judgment will be dreadful; that none may think that it is a matter of small importance. Accordingly, he describes that horror in strong language, that the wicked may fear, and that believers, on the other hand, may keep themselves holy and chaste, and may withdraw from the society of the wicked. Yet let them endure patiently the unjust and cruel attacks of enemies, till the armed avenger come forth front heaven. [1] And many shall be the slain of Jehovah. He threatens the destruction of all men, so that there may be a prodigious mass of corpses. And he expressly added this, because ungodliness reigned everywhere, and believers were subjected to a dangerous temptation on account of the prosperity of the wicked; for such is the fickleness of our minds, that we allow ourselves to be led away by a bad custom, and are alarmed by a multitude, as if it were sufficient for restraining the hand of God. This sinful fear the Prophet corrects by reminding' them, that the more ungodliness shall abound, and the greater the number of wicked men, so much the more will the wrath of the Lord be kindled, that he may make a greater and more extensive slaughter; and the multitude and conspiracy of the ungodly shall not hinder him from carrying them away by the same ruin.

Footnotes

1 - "Jusques a tant que Dieu vienne du ciel a main armee pour en faire vengeance." "Till God come from heaven with an armed force, to take vengeance on them."

For by fire and by his sword - The sword is an instrument by which punishment is executed (see the notes at Isaiah 34:5; compare Romans 13:4).
Will he plead with all flesh - Or rather, he will judge (נשׁפט nı̂shephaṭ), that is, he will execute his purposes of vengeance on all the human race. Of course, only that part is intended who ought to be subject to punishment; that is, all his foes.
And the slain of the Lord shall be many - The number of those who shall be consigned to woe shall be immense - though in the winding up of the great drama at the close of the world, there is reason to hopethat a large proportion of the race, taken as a whole, will be saved. Of past generations, indeed, there is no just ground of such hope; of the present generation there is no such prospect. But brighter and happier times are to come. The true religion is to spread over all the world, and for a long period is to prevail; and the hope is, that during that long period the multitude of true converts will be so great as to leave the whole number who are lost, compared with those who are saved, much less than is commonly supposed. Still the aggregate of those who are lost, 'the slain of the Lord,' will be vast. This description I regard as having reference to the coming of the Lord to judgment (compare 2-Thessalonians 1:8); or if it refer to any other manifestation of Yahweh for judgment, like the destruction of Jerusalem by the Romans, it has a strong resemblance to the final judgment; and, like the description of that by the Saviour Matt. 24, the language is such as naturally to suggest, and to be applicable to, the final judgment of mankind.

For by fire, and by his sword, will the Lord plead with all flesh,.... With the Mahometans, the Turks, the Ottoman empire, against whom he will call for a sword, and will rain upon them fire and brimstone, signified by Gog and Magog, Ezekiel 38:22 and with the other antichristian powers at the battle of Armageddon; and when the fourth vial will be poured upon the sun, and men will be scorched with fire; see Revelation 16:8,
and the slain of the Lord shall be many; that is, those that will be slain by the Lord, both in the attempt of the Turks to recover the land of Canaan out of the hands of the Jews, possessed of it; whose numbers of slain will be so many, that the burying of them will last seven months, Ezekiel 39:12 and in the battle between the Christian princes, Christ at the head of them, and the antichristian armies, led on by the beast and the kings of the earth; when the fowls of the air will be invited to the great supper of the Lord, to eat the flesh of kings, captains, and mighty men, so great will the slaughter be, Revelation 19:17, see also Isaiah 11:13.

Rather, "With fire will Jehovah judge, and with His sword (He will judge) all flesh." The parallelism and collocation of the Hebrew words favor this (Isaiah 65:12).
all flesh--that is, all who are the objects of His wrath. The godly shall be hidden by the Lord in a place of safety away from the scene of judgment (Isaiah 26:20-21; Psalm 31:20; 1-Thessalonians 4:16-17).

Jehovah appears with these warlike terrors because He is coming for a great judgment. "For in the midst of fire Jehovah holds judgment, and in the midst of His sword with all flesh; and great will be the multitude of those pierced through by Jehovah." The fire, which is here introduced as the medium of judgment, points to destructive occurrences of nature, and the sword to destructive occurrences of history. At the same time all the emphasis is laid here, as in Isaiah 34:5-6 (cf., Isaiah 27:1), upon the direct action of Jehovah Himself. The parallelism in Isaiah 66:16 is progressive. Nishpat 'ēth, "to go into judgment with a person," as in Ezekiel 38:22 (cf., עם in Isaiah 3:14, Joel 3:2; 2-Chronicles 22:8; μετά, Luke 11:31-32). We find a resemblance to Isaiah 66:16 in Zephaniah 2:12, and this is not the only resemblance to our prophecy in that strongly reproductive prophet.

Plead - God at first pleads with sinners by words, but if he cannot so prevail, he will plead with them in a way by which he will overcome; by fire, pestilence and blood. All flesh - Thus he threatens to do with all the wicked Jews. The slain - Those whom God should cause to be slain.