For thus hath the Lord said unto me, Go, set a watchman, let him declare what he seeth. And he saw a chariot with a couple of horsemen, a chariot of asses, and a chariot of camels; and he hearkened diligently with much heed: And he cried, A lion: My lord, I stand continually upon the watchtower in the daytime, and I am set in my ward whole nights: 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. O my threshing, and the corn of my floor: that which I have heard of the LORD of hosts, the God of Israel, have I declared unto you.
The Lord instructed Isaiah to appoint a watchman to describe the attacking hordes, especially the numberless cavalry units. After waiting for days and nights, he reported the advance of riders in pairs. This may suggest the Medes and the Persians. Then, with a lion-like roar, he announced the fall of Babylon and her idolatrous religion. The announcement is a message of comfort to Israel, a nation that has been threshed and winnowed by Babylon. It is good to remember that this prophecy was made about two hundred years before Babylon’s fall.