John Calvin's Bible Commentary
Jeremiah 51:31
This also was fulfilled according to the testimony of heathen authors, as well as of Daniel. They do not indeed repeat these words, but according to the whole tenor of history we may easily conclude that messengers ran here and there, for the Babylonians never thought that the enemy could so suddenly penetrate into the city, for there was no entrance. We have seen how high the walls were, for there were no muskets then, and the walls could not have been beaten down. There were indeed battering-rams; but what was the breadth of the walls? even fifty feet, as already stated, so that four horses abreast could pass without coming into contact. There was then no battering-ram that could throw down walls so thick. As to the fords, the thing seemed incredible; so that they kept a feast in perfect security. In such an irruption, what our Prophet testifies here must have necessarily happened. But it is quite evident that he was the instrument of the Holy Spirit; for Cyrus was not as yet born when this prophecy was announced. We hence then know, that the holy man was guided from above, and that what he said was not produced in his own head, but was really celestial; for he could not have divined any such thing, nor was it through probable conjecture that he was able thus to speak and lead the Jews, as it were, into the very scene itself.
Nor is there a doubt but that this authority was afterwards confirmed when the fathers told their children, “So have we heard from the mouth of the Prophet what we now see with our eyes; and yet no man could have conjectured any such thing, nor have discovered it by reason or clearsightedness: hence Jeremiah must have necessarily been taught by the Spirit of God.” This, then, is the reason why God designed that the destruction of Babylon should be, as we see, so graphically described.
He then says, A runner ran to meet a runner, and then, a messenger to meet a messenger, to tell the king of Babylon that his city was taken at its extremity ? (93) Had this been said of a small city, it might have appeared ridiculous: why are these runners? one might say. But it has been sufficiently shown, that so extensive was that city, that runners, passing through many fields, might have come to the king, and convey the news that the city was taken at one of its extremities. And heathen writers cannot sufficiently eulogize the contrivance and skill of Cyrus, that, he thus took possession of so great a city; for he might have only secured one half of it, and Belshazzar might have retained the other half, and might have bravely contested with Cyrus and all his forces; and he would have no doubt overcome him, had it not been for the wonderful and unusual expedition of Cyrus. This haste, then, or expedition of Cyrus, is what the Prophet now sets forth, when he says that messengers ran to the king to tell him that the city was taken He now adds, respecting other things, what no one could have divined, —