Albert Barnes Commentary 2 Kings 20:14

"Then came Isaiah the prophet unto king Hezekiah, and said unto him, What said these men? and from whence came they unto thee? And Hezekiah said, They are come from a far country, even from Babylon." — 2 Kings 20:14 (ASV)

Hezekiah did not answer Isaiah’s first question, “What said these men?” but only his second. He probably knew that Isaiah would oppose any reliance on an “arm of flesh.”

Babylon was now revealed to the Jews for the first time as an actual world power that could affect them politically. Until then, even the prophets had spoken little of the great southern city; up to this point, it had been little more to them than Tyre, Tarshish, or any other rich and powerful idolatrous city.

From then on, this was completely changed. The prophetic utterance of Isaiah on this occasion (2 Kings 20:16–18) was never forgotten, nor could it be. He followed it up with a burst of prophecy in Isaiah 40–66, in which Babylon completely usurps Assyria's place as Israel’s enemy. With the captivity assumed as a certainty, the people's hopes were directed beyond it toward the Return.

Other prophets took up this theme and repeated it (Habakkuk 1:6–11; Habakkuk 2:5–8; Micah 4:10). Thus, from that point on, Babylon—instead of Assyria—became the great object of the nation’s fear and hatred.