John Calvin Commentary Jeremiah 51:31

"One post shall run to meet another, and one messenger to met another, to show the king of Babylon that his city is taken on every quarter:" — Jeremiah 51:31 (ASV)

This was also fulfilled according to the testimony of pagan authors, as well as of Daniel. They do not indeed repeat these words, but according to the whole course of history, we may easily conclude that messengers ran to and fro, for the Babylonians never thought that the enemy could so suddenly penetrate the city, for there was no way in.

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 width of the walls? Fully fifty feet, as previously 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. Regarding the fords, such an approach seemed incredible, so they held a feast in perfect security. In such a sudden attack, what our Prophet testifies to here must necessarily have happened. But it is quite evident that he was the instrument of the Holy Spirit, for Cyrus was not yet born when this prophecy was announced.

Therefore, we know that the holy man was guided from above, and that what he said did not originate in his own mind but was truly heavenly. For he could not have divined any such thing, nor was it through probable conjecture that he was able to speak in this way and lead the Jews, as it were, into the very scene itself.

There is no doubt that this authority was later confirmed when the fathers told their children, “This is what we heard from the mouth of the Prophet, which we now see with our eyes; and yet no one could have conjectured any such thing, nor have discovered it by reason or discernment: therefore, Jeremiah must necessarily have been taught by the Spirit of God.” This, then, is the reason why God intended 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? 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 the city was so extensive that runners, passing through many fields, might have come to the king and conveyed the news that the city was taken at one of its extremities.

Pagan writers cannot sufficiently praise the ingenuity and skill of Cyrus, in 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; indeed, Belshazzar would undoubtedly have overcome Cyrus, had it not been for the wonderful and unusual swiftness of Cyrus.

This haste, then, or swiftness 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, regarding other things, what no one could have divined—