Isaiah 7:19
And they shall come, and shall rest all of them in the desolate valleys, and in the holes of the rocks, and upon all thorns, and upon all bushes. And they shall come, and shall rest all of them in the desolate valleys, and in the holes of the rocks, and upon all thorns, and upon all bushes.
Isaiah 7:19 belongs to a prophecy spoken during the reign of King Ahaz, when sin and darkness prevailed among God's people. The passage around it is centered on Ahaz and his stubbornness. It pictures invading forces coming and spreading through the land to rest there. Their resting and shelter are in desolate valleys, in holes of the rocks, and upon all thorns and bushes, where they settle throughout the land.
It records one of the evils God has brought upon men in the past. None of those past evils has equaled what is to come in the great day of the Lord. That coming day is emphatically the great day of His wrath. That same setting provides the context for a prophecy about the coming Deliverer, so that hope remained for the future. The verse itself gives no further explanation beyond that setting.