John Calvin on Jeremiah 51:2

Here he explains himself more clearly, without the metaphor he had used. He no longer uses the similitude of wind when he declares that he would send fanners At the same time some take זארים, zarim, in the sense of aliens, who would banish her; but this would be harsh. I then doubt not but that the Prophet alludes to the wind before mentioned. He does not indeed continue that metaphor; but yet what he says corresponds with it. Instead of wind he now mentions fanners, or winnowers; but this cannot be understood except of enemies. A clearer explanation is still found in the word empty, after having said that the Persians and the Medes would fan or winnow Babylon. He compares her, no doubt, to chaff. As then the chaff, when ventilated, falls on the ground, so he says a similar thing would happen to the Babylonians.

But he adds, And shall make empty her land, that is, the land of Babylon. He says that the whole country would be so plundered, that nothing would be left remaining. And he confirms this declaration, because they shall be, he says, around her. By this expression he intimates that there would be no escape for the Chaldeans.

It often happens that men stealthily escape, when pressed by their enemies; for though enemies may watch all passages, yet they often do not find out all hiding-places. But the Prophet says, that their enemies would so surround them, that the Chaldeans would not be able to take with them anything which they might save from their enemies’ hands. He adds, in the day of evil. By this phrase he intimates again, that the Chaldeans were already devoted by God to destruction. It is, then, the same thing as though he had said, that as soon as her enemies came, it would be all over with Babylon and the whole nation, — how so? for it would be the day of her utter ruin. It follows, —

Jeremiah 51:3

3. Against him that bendeth let the archer bend his bow, and against him that lifteth himself up in his brigandine: and spare ye not her young men; destroy ye utterly all her host.

3. Ad tendentem qui tendit arcum suum ידרך est hic vox supervacua, qui tendit igitur arcum suum,) et (copula hic abundat;) ne parcatis electis ejus, interficite omnem exercitum ejus.