2 Kings 19:31
For out of Jerusalem shall go forth a remnant, and they that escape out of mount Zion: the zeal of the LORD of hosts shall do this. For out of Jerusalem shall go forth a remnant, and they that escape out of mount Zion: the zeal of the LORD of hosts shall do this.
After an army of occupation had laid waste the land of Judah, an escaped remnant of the house of Judah preserved in Jerusalem and on Mount Zion would go forth and grow again, taking root downward and bearing fruit upward. Their survival was not by their own power, for God promised to keep them alive and to provide miraculously for their needs in the devastated land.
That provision would come in stages, with the people eating that year what grows of itself, and in the second year what springs from the same, and then in the third year sowing and reaping and planting vineyards and eating the fruit of them. At the same time God Himself would defend Jerusalem to save it for His own sake and for David's sake. Therefore the king of Assyria would not come into the city, nor shoot an arrow there, nor come before it with shield, nor cast a bank against it, but would return by the way he came. The zeal of the Lord of hosts would accomplish all of this, both the preservation and increase of the remnant and the deliverance of the city.