Contradiction with 1 Corinthians 8:4
Contradicts because Isaiah 21:9 declares the fall of Babylon and its idols, whereas 1 Corinthians 8:4 states there is no other God but one, implying idols have no real existence.
1 Corinthians 8:4: As concerning therefore the eating of those things that are offered in sacrifice unto idols, we know that an idol [is] nothing in the world, and that [there is] none other God but one.
Contradiction with Isaiah 14:4
Contradicts because Isaiah 21:9 mentions the fall of Babylon, whereas Isaiah 14:4 speaks of the downfall of the king of Babylon in a taunting manner, suggesting a focus on the ruler rather than the city itself.
Isaiah 14:4: That thou shalt take up this proverb against the king of Babylon, and say, How hath the oppressor ceased! the golden city ceased! [proverb: or, taunting speech] [golden...: or, exactress of gold]
Contradiction with Jeremiah 50:39
Contradicts because while Isaiah 21:9 indicates a fall, Jeremiah 50:39 describes a desolation that lasts forever, suggesting a more permanent state rather than just a fall.
Jeremiah 50:39: Therefore the wild beasts of the desert with the wild beasts of the islands shall dwell [there], and the owls shall dwell therein: and it shall be no more inhabited for ever; neither shall it be dwelt in from generation to generation.
Contradiction with Revelation 17:5-6
Contradicts with Isaiah 21:9's depiction of Babylon's fall due to idol worship, whereas Revelation 17:5-6 describes Babylon as an entity in power and causing harm.
Revelation 17:5-6: And upon her forehead [was] a name written, MYSTERY, BABYLON THE GREAT, THE MOTHER OF HARLOTS AND ABOMINATIONS OF THE EARTH. [harlots: or, fornications]
Contradiction with Habakkuk 1:6-7
Contradicts because Isaiah 21:9 speaks of the destruction of Babylon, while Habakkuk 1:6-7 describes the rise of the Chaldeans (Babylonians) as a fierce and terrifying nation.
Habakkuk 1:6-7: For, lo, I raise up the Chaldeans, [that] bitter and hasty nation, which shall march through the breadth of the land, to possess the dwellingplaces [that are] not theirs. [breadth: Heb. breadths]