John Calvin on Jeremiah 49:21

The Prophet in many words dwells on the same thing, in itself sufficiently clear; but as it was not easy to convince the Jews of what had been already said of the destruction of the Idumeans, the Prophet continues the same subject. He then says that the earth trembled at the sound of their fall By these words he means that such would be the calamity, that it would terrify all neighboring countries: as when a great mass falls, the earth shakes, so the fall of the Idumeans, who had long gloried in their wealth, could not but strike all their neighbors with terror. Lest the Jews should think that incredible which had been said, the Prophet says, that though the earth should tremble, yet God would overthrow that nation.

He then adds, the cry of their voice was heard at the Red Sea The literal rendering is, —

The cry — at the Red Sea was heard its sound.

It is an instance of the nominative case absolute. — Ed. This sea, called now Red, was at some distance. The word סוף, suph, properly signifies weedy, a name given to it on account of the bulrushes it produced; but the sea that is meant, is what is now called the Red Sea. I have said that the distance between these places was considerable, and what the Prophet means is, that so great and so dreadful would be the shaking of the land of Edom, that its noise would make this sea to tremble, though it was at some distance. It follows —

Jeremiah 49:22

22. Behold, he shall come up and fly as the eagle, and spread his wings over Bozrah: and at that day shall the heart of the mighty men of Edom be as the heart of a woman in her pangs.

22. Ecce tanquam aquila ascendet, et volabit et expander alas suas super Bosra, et erit cor fortium Edom die illo sicuti cor mulieris anxiae.