"'You said, "No, we will flee on horses." Therefore you will flee! You said, "We will ride off on swift horses." Therefore your pursuers will be swift! A thousand will flee at the threat of one; at the threat of five you will all flee away, till you are left like a flagstaff on a mountaintop, like a banner on a hill.'" NIV translation
Isaiah continues to describe what happened to the northern kingdom when they chose to run to Egypt for help instead of repenting and trusting in the Lord. He refers to Deuteronomy 32:30 and the fact that Moses had predicted that Israel would turn to idolatry instead of trusting in God. With the reference to the flagstaff and banner, Isaiah spoke of the fact that Israel's lack of faith and the resulting exile would be a sign (testimony) to Judah and Jerusalem.
"Yet the Lord longs to be gracious to you; therefore he will rise up to show you compassion. For the Lord is a God of justice. Blessed are all who wait for him!" NIV translation
Even as God handed Israel over to the Assyrians, there was still the promise of mercy and compassion because they were His chosen people. Once they were in exile, they would have no choice but to wait and trust in God to deliver them. Those who remembered that fact did not have to worry about the future as they could be confident that God would keep His promises. Those who did not, would continue to worry about what was going to happen to them.
So, what does this have to do with us as Christians in the world today? We, too, can learn from the history of Israel. When we are faced with difficult situations, we can choose to trust God and wait on Him or we can try to run to others for help. If we wait on the Lord and see His deliverance, we will grow in our faith and it will be easier to trust in Him when a bigger challenge comes along. If we run to others for help, they might help us with our present trouble but we cannot be sure that they will be there every time. At some point, they will let us down.