2 Kings 19:30

And the remnant that is escaped of the house of Judah shall yet again take root downward, and bear fruit upward.

After the land of Judah had been laid waste by an occupying army, a future was promised for the escaped survivors of the house of Judah. To take root downward and bear fruit upward meant they would again become firmly established and grow productive. The escaped remnant were in Jerusalem and Mount Zion, and this renewal would go forth out of Jerusalem and out of Mount Zion. This renewed rootedness and fruitfulness would be accomplished by the zeal of the Lord of hosts.

God joined the promise with miraculous provision of food for two years until normal sowing, reaping, and vineyard planting could resume in the third year. Specifically, the people would eat what grew by itself in the first year and what sprang from the same in the second year, then in the third year they would sow and reap, plant vineyards, and eat their fruit. God also joined the promise with defense of Jerusalem to save it for His own sake and for David's sake, so that the king of Assyria would not enter the city. In particular, the king of Assyria would not come into the city, shoot an arrow there, come before it with shield, or cast a bank against it, but would return by the same way he came.