John Calvin Commentary Jeremiah 48:28

"O ye inhabitants of Moab, leave the cities, and dwell in the rock; and be like the dove that maketh her nest over the mouth of the abyss." — Jeremiah 48:28 (ASV)

Here Jeremiah denounces exile on the Moabites, as if he had said that the desolation of their land would be so great that they would be forced as wanderers to flee here and there. That he commands them to leave their cities, is not done in the same way as when God commands His people what is right. Instead, he only shows that he was armed with the sword of God, not only to speak with his mouth but also to perform what he foretells. For the execution should not be separated from the prophecies, because the hand of God is joined with His mouth. Therefore, when God announces anything through His servants, the fulfillment is also included, as has been stated.

This is the meaning of the words, Leave the cities, and dwell among the rocks; that is, hide yourselves in hiding places, for no habitable land will afford you rest or be a convenient place for refuge. And they shall be, he says, like a dove which makes a nest in remote places beyond the clefts of the rocks, or stones. He means the most deserted places. It is as if he had said that it would not be a simple exile that God would allot to the Moabites, but that they would be taken away to regions unknown and deserted by people.