Call unto me, and I will answer thee, and shew thee great and mighty things, which thou knowest not.
Call unto me ... I will answer - (Jeremiah 29:12; Psalms 91:15). Jeremiah, as the representative of the people of God, is urged by God to pray for that which God has determined to grant-namely, the restoration. God's promises are not to slacken, but to quicken the prayers of His people (Psalms 132:13; Psalms 132:17; Isaiah 62:6-7).
Mighty things - Hebrew [uwbªtsurowt], properly, things fortified, 'inaccessible things' - i:e., incredible, hard to man's understanding (Maurer) - namely, the restoration of the Jews, an event despaired of. 'Hidden,' or 'recondite' (Piscator).
Which thou knowest not - yet God had revealed those things to Jeremiah, but the unbelief of the people in rejecting the grace of God had caused him to forget God's promise, as though the case of the people admitted of no remedy.
Concerning the houses ... thrown down by the mounts - namely, by the missiles cast from the besiegers' mounds (Jeremiah 32:24); "and by the sword" follows properly, as after missiles had prepared the way, the foe next advanced to close quarters 'with the sword.'