The expansion of the New Covenant to the nations is a glorious reality. The fact that God chose a certain people (Israel) to be His own and to bless and to act on their behalf is unspeakably gracious and wonderful in and of itself, but thankfully (for my sake) His grace did not stop there. In the New Covenant, the old enemies of God are called into His family, and the results have been astounding. In the Gospels, Jesus starts many of His parables by saying, "The Kingdom of God is like..." or "The Kingdom of Heaven is like...", and several of these parables speak of the great growth of God's Kingdom. There is the one about the mustard seed, where Jesus explains that the Kingdom will start very small in relation to other kingdoms and then grow to be very large in relation to other kingdoms. There is the one about the leaven, where Jesus explains that from a humble beginning the Kingdom will spread throughout the entire world. These parables parallel the prophet Daniel's description of the growth of the same Kingdom in Daniel 2:34-35, 44-45 where he descibes a stone cut by no human hand that would start small and then grow to be a mountain that would fill the whole earth.
These parables and prophecies all refer to the growth and global saturation of Christ's Kingdom: the Church. And as we look back through church history, we find a very literal fulfillment of these promises in the spread of the gospel to all the nations. What began with a little over a hundred believers in Jerusalem in the first century A.D. rapidly multiplied and filled the ancient world, eventually even dominating the secular state. And now, twenty centuries later, the good news of the salvation that is provided in Jesus Christ has spread to every land on the planet, and the leaven of the Kingdom continues to infect even the darkest corners of the globe.
So what could the future look like if the gospel continues to spread and the church continues to grow? How far could it go before Jesus returns?
There is an interesting picture in Isaiah 19 of this exact situation. In verses 16-25, God describes the glorious salvation of two of Israel's former enemies: Egypt and Assyria. A curious statement is made there in verse 18: "In that day there will be five cities in the land of Egypt that speak the language of Canaan and swear allegiance to the LORD of hosts. One of these will be called the City of Destruction." Some Bible scholars see here an indication that perhaps as the gospel spreads throughout the world, it may eventually get to the point where five out of six cities would declare themselves for the Lord. In other words, we could be looking at a possible 83% conversion rate world-wide sometime in the future.
What kind of wonders of peace and joy might await the generation that sees the gospel affect that much of the world's population? There's no doubt that Jesus has a beautiful future prepared for His church. Our goal as Christians should be no less than seeing the kingdom of this world becomming the Kingdom of our God. We're promised that it will happen. That should give us the courage and the energy to work toward its fulfillment!