John Calvin on Jeremiah 48:40

Here again he introduces God’s name, for it was necessary to confirm an incredible prophecy by his authority. “God is he,” he says, “who declares that enemies will come, who will fly through all the land of Moab.” He now compares the Chaldeans to eagles; and there is here a name understood which is not expressed. Fly will he like an eagle, that is, the king of Babylon with his army.

The sum of what is said then is, that however widely extended might be the country of Moab, yet there would be no corner into which the Chaldeans would not penetrate, because they would nearly equal the eagles in swiftness. Hence he adds, They will extend their wings, not to cherish, as eagles spread their wings over their young ones; but by extension he means, that they would seize on all the land of Moab; so that hiding places would be sought in vain, because the Chaldeans would from one part to another take possession of every place, however remote the Moabites might think it to be, and however they might hope its distance would render it safe. He afterwards adds, —

Jeremiah 48:41

41. Kerioth is taken, and the strong holds are surprised, and the mighty men’s hearts in Moab at that day shall be as the heart of a woman in her pangs.

41. Captae sunt urbes (est hic etiam mutatio numeri, sed dura esset translatio ad verbum, ideo satis est sensum tenere; captae ergo sunt urbes, hoc est, unaquaeque urbs capta est, deinde,) arces (vel, propugnacula) comprehensa sunt (est iterum mutatio numeri,) et fuit cor virorum Moab in die illa tanquam cor mulieris quae angitur (vel, premitur anxietate.)