Isaiah 21:9

9 Look, here comes a man in a chariot with a team of horses. And he gives back the answer: ‘Babylon has fallen, has fallen! All the images of its gods lie shattered on the ground!’ ”

Read Isaiah 21:9 Using Other Translations

And, behold, here cometh a chariot of men, with a couple of horsemen. And he answered and said, Babylon is fallen, is fallen; and all the graven images of her gods he hath broken unto the ground.
And behold, here come riders, horsemen in pairs!" And he answered, "Fallen, fallen is Babylon; and all the carved images of her gods he has shattered to the ground."
Now at last—look! Here comes a man in a chariot with a pair of horses!” Then the watchman said, “Babylon is fallen, fallen! All the idols of Babylon lie broken on the ground!”

What does Isaiah 21:9 mean?

John Gill's Exposition of the Bible
Isaiah 21:9

And, behold, here cometh a chariot of men
Or "of a man" F24; a chariot with a man in it, Cyrus or Darius: [with] a couple of horsemen;
the army of the Medes and Persians, with their two leaders or generals, as before; only now seen nearer the city, just entering into it; for so the word may be rendered, "goeth", or "is gone in a chariot": and he answered, and said;
either the watchman, upon seeing the chariot and horsemen go into the city; or one of the horsemen that went in; so the Syriac and Arabic versions; or rather the prophet, and the Lord by him: Babylon is fallen, is fallen:
which is repeated to show the certainty of it. The same words are used of the fall of mystical Babylon, ( Revelation 14:8 ) ( 18:2 ) . The Targum is,

``it is fallen, and also it shall be, that Babylon shall fall;''
that is, a second time, and hereafter: and so Jarchi and Kimchi interpret it of two falls, one by the Medes and Persians, and the other by the hand of heaven, or God himself: literal Babylon fell by the former; mystical Babylon will fall by the latter, even by the breath of Christ's mouth, and the brightness of his coming: and all the graven images of her gods he hath broken unto the
ground;
either Cyrus or Darius, who might do this, not from any detestation of them, but for the sake of the gold, and silver, and riches, that were about them; or rather the Lord by them, and so put an end to idolatry; as will be, when mystical Babylon is destroyed.
FOOTNOTES:

F24 (vya bkr) "currus viri", Pagninus, Montanus.
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