Jamieson, Fausset and Brown on Jeremiah 48:45

45. under ... shadow of Heshbon--They thought that they would be safe in Heshbon.

because of the force--that is, "they that fled because of the force" of the enemy: they that fled from it. Glassius translates, "through want of strength." So the Hebrew particle is translated (Psa 109:24), "faileth of fatness," that is, "faileth through want of fatness"; also La 4:9.

but a fire, &c.--copied in part from Sihon's hymn of victory (Nu 21:27, 28). The old "proverb" shall hold good again. As in ancient times Sihon, king of the Amorites, issued forth from his city, Heshbon, as a devouring "flame" and consumed Moab, so now the Chaldeans, making Heshbon their starting-point, shall advance to the destruction of Moab.

midst of Sihon--that is, the city of Sihon.

corner of Moab--that is, Moab from one corner to the other.

crown of ... head--the most elevated points of Moab. Making some alterations, he here copies Balaam's prophecy (Nu 24:17). Margin there translates "princes" for corners; if so, "crown of ... head" here refers to the nobles.

tumultuous ones--sons of tumult; those who have tumultuously revolted from Babylon. Heshbon passed from the Amorite to the Israelite sway. Moab had wrested it from Israel and helped the Chaldeans against the Jews; but revolting from Babylon, they brought ruin on themselves in turn.