The LORD hath purposed to destroy the wall of the daughter of Zion: he hath stretched out a line, he hath not withdrawn his hand from destroying: therefore he made the rampart and the wall to lament; they languished together.
God has decided to demolish Zion's city wall. He has drawn a line, but hasn't stopped destroying. That's why the fortification and wall are sad and weak. They're hurting together.