Jeremiah 48:45: Verse 45
They that fled stood under the shadow of Heshbon - Heshbon being a fortified place, they who were worsted in the fight fled to it, and rallied under its walls; but, instead of safety, they found themselves disappointed, betrayed, and ruined. See Jer 48:2 (note), and the note there.
But a fire shall come forth out of Heshbon - Jeremiah has borrowed this part of his discourse from an ancient poet quoted by Moses, Num 21:28 (note); where see the notes.
The crown of the head - The choicest persons of the whole nation.