Albert Barnes Commentary 2 Kings 19:30

"And the remnant that is escaped of the house of Judah shall again take root downward, and bear fruit upward." — 2 Kings 19:30 (ASV)

The remnant that has escaped - Terrible ravages seem to have been committed in the first attack (see note on 2 Kings 18:13). And though the second invasion was comparatively harmless, it still probably fell heavily on the cities of the west and the southwest. Thus, the “escaped” were only “a remnant.”

Bear fruit upward - The flourishing time of Josiah is the special fulfillment of this prophecy (2 Kings 23:15–20).