Just in case we thought it was sufficient to stand only in reverence or awe or respect of Him, Isaiah adds, "Let Him be your dread!" God is asking, in effect, "Of whom are you more afraid, the Assyrians or Me?"
In The Interpreter's Bible Commentary appears an interesting comment regarding this passage. The editors saw clearly that God was instructing Isaiah to turn away from the bulk of the Israelites and aim his message at a tiny remnant of people who were willing to be obedient and faithful in response to God. He tells the prophet to reject the main body and pay attention to a small group, the remnant that desires to be faithful to God. He said, "I will become a snare, a trap, to those who are turning away from Me. They will stumble as a result of not having the fear of God and because of their faithlessness."
God does not seem the least bit worried that His people should dread Him. Indeed, this dread, rather than hindering a proper relationship with Him, is advanced as producing a positive benefit. He becomes a sanctuary, a place of abode, to which his people can run for safety. He is a place of safety for those who fear Him!
John W. Ritenbaugh
The Fear of God