Albert Barnes' Notes on the Whole Bible - 2 Kings 19:30
The remnant that is escaped - Terrible ravages seem to have been committed in the first attack (2 Kings 18:13 note). And though the second invasion was comparatively harmless, yet it probably fell heavily on the cities of the west and the southwest. Thus the “escaped” were but “a remnant.”Bear fruit upward - The flourishing time of Josiah is the special fulfillment of this prophecy 2 Kings 23:15-20. read more
The Pulpit Commentary - 2 Kings 19:31
For out of Jerusalem shall go forth a remnant. The march of Sennacherib and the raid of Rabshakeh had driven the mass of the escaped population of Judaea to take refuge within the walls of Jerusalem, from which, on the retirement of the invaders, they would gladly "go forth," to recultivate their lands ( 2 Kings 19:29 ) and restore their ruined homes. And they that escape —rather, that shall escape— out of Mount Zion —"Mount Zion" is a variant for Jerusalem, as in 2 Kings 19:21 ,... read more