Their heart - That of the inhabitants of Jerusalem. The prophet bids the wall, as the representative of the people who had dwelt secure under its protection, shed floods of tears on their behalf. Broken up by the enemy, it could be their guardian no longer, but by its ruins it might still cry unto the Lord in their behalf.
A river - Or, a brook or torrent.
Rest - Properly, the torpor and numbness which follows upon excessive grief.
Apple of thine eye - See Psalms 17:8 note.