C. F. Keil and Franz Delitzsch on Jeremiah 48:28

Jer 48:28

A transition is now made from figurative to literal language, and Moab is summoned to leave the cities and take refuge in inaccessible rocks, because he will not be able to offer resistance to the enemy; cf. Jer 48:6 and Jer 48:9. "Like a dove that builds its nest over deep crevices." The reference is to wild pigeons, which occur in large numbers in Palestine, and make their nests in the clefts of high rocks (Sol 2:14) even at the present day, e.g., in the wilderness of Engedi; cf. Robinson’s Palestine, ii. 203. בּעברי , lit., "on the other side of the mouth of the deep pit," or of the abyss, i.e., over the yawning hollows. בּעברי is a poetic form for בּעבר, as in Isa 7:20. The humiliation of Moab finds its justification in what is brought out in Jer 48:29., his boundless pride and hatred against Israel.