Isaiah revealed the reason for this defeat. In the day of God"s judgment (cf. Isaiah 17:7; Isaiah 17:9), Jacob"s prosperity would become lean, as when one grows old and loses his former strength, because of her unbelief: her lack of trust in God. She would experience a thorough reaping of her population, as reapers harvested abundant grain crops in the productive valley of Rephaim near Jerusalem. Yet a remnant would survive, like the few olives or fruits left after a harvest for gleaners to collect. This is what Yahweh, the God who had pledged Himself to Israel, declared. [source][source][source]
"Judah need not fear her neighbors; it is God with whom she should come to terms." [1][source]