John Calvin Commentary Jeremiah 48:19

"O inhabitant of Aroer, stand by the way, and watch: ask him that fleeth, and her that escapeth; say, What hath been done?" — Jeremiah 48:19 (ASV)

We have stated elsewhere why the prophets, in describing calamities, spoke in such an elevated style; for their object was not to seek fame or the praise of eloquence. These were not rhetorical ornaments that the prophets used; instead, they necessarily spoke in a lofty style about the punishments that awaited the ungodly, because the hardness of their hearts was such that they did not hesitate to despise God’s threats, or to regard them as fables.

So that God’s threats might then penetrate into people's hearts, it was necessary to exaggerate them by means of various comparisons, as is done here and in many places. We should, at the same time, bear in mind what I have said: that the Prophet had regard for his own people.

Since the Moabites were like a hidden treasure, the Jews could never have thought it possible that the Chaldeans would eventually make an inroad there. But the Prophet declares that this event was so certain, it was as if it were seen by their own eyes. Therefore, to lead the Jews to the very scene itself, God's judgments are not only described here but are, as it were, painted.

Stand, he says, on the way, and look, thou inhabitant of Aroer. This was another city of the Moabites, mentioned in many places; and then he mentions others, as we shall see. Ask him, he says, who fleeth and her who escapes.

He indeed changes the gender of the nouns; but when he mentions many, and then one person, he did this for amplification, because on the one hand, he wished to show that the number of exiles would be so great that the whole land would become empty; and then, on the other hand, when he says that this person and that person would flee, he means that they would be so scattered that they would not go in groups; rather, as is usual in a state of disorder, one would flee on this side, and another on the other side.

Ask him who fleeth, or as we may render the words, Ask all who flee; and then, ask her who escapes. This is because not only men but also women would flee, so that no sex would be spared. In short, he intimates that those who lived in well-fortified cities would be in great anxiety on seeing enemies irresistibly advancing through every part of the country.