Keil & Delitzsch

"For the mountains may depart, and the hills may shake; my grace will not depart from thee, and my covenant of peace will not shake, saith Jehovah who hath compassion on thee." Jehovah's grace and covenant of peace (cf., Num 25:12) stand as firm as the mountains of God (Psa 36:7), without departing from Jerusalem (מאתּך instead of the usual מאתּך) and without shaking; and they will be fulfilled. This fulfilment will not take place either by force or by enchantment; but the church which is to be glorified must pass through sufferings, until it has attained the form which answers to the glory promised to it on oath. And this will also take place; for the old Jerusalem will come forth as a new one out of the furnace of affliction.