The Lord will rise up as he did at Mount Perazim, he will rouse himself as in the Valley of Gibeon - to do his work, his strange work, and perform his task, his alien task.
Isaiah had warned the leaders of Jerusalem that their military and their religion would not save them. Now, he explains why and gives two examples from their history. We are reminded that, throughout the Bible, the number two is associated with witnesses and was required to establish that something was truth. At Mount Perazim, which means "breaks out", God had fought against the Philistines on behalf of David and given him the victory. In the Valley of Gibeon, God made the sun stand still as Joshua was facing five kings in battle. This gave him the necessary time to completely destroy them. These two examples show God intervening on behalf of His people so, why would this bring terror to the people of Jerusalem? Isaiah goes on to explain that the work that God was going to do was "strange" and "alien" which is from the Hebrew word "zuwr" and basically means "foreign". The "foreign" work that God was going to do was the fact that He was not going to defend Jerusalem or Judah and, in fact, He was going to side with the Babylonians to judge the land. This is "foreign" to God as He wants to bless His people and it would cause terror to His people when they see that God is against them. So, what does this have to do with us as Christians in the world today? As in Isaiah's day, more and more people do not see a need for God in their lives or, if they do, it is merely a religious obligation. This will only be tolerated for a certain period of time and then God will bring judgment on the land and the people. God used the Babylonians as His instrument of judgment in Isaiah's day and, in the last days, He will use Satan and his world system to persecute His people. This again is "foreign" to God but the purpose is to bring people to a point of repentance so that they can be rescued. The good news is that, during this period of time, the greatest "revival" that the world has ever seen will happen.