I am not sure who first said it, but there is a quote floating around: "The church is the only institution that exists for the sake of non-members."
Karl Barth said something similar when he defined church as "community for the sake of the world." I would modify that slightly to "Christ-centered community for the sake of the world."
God's purpose for His people has always included an evangelistic component. Just look at the covenant promise to Abraham, restated many times to him and to Isaac and to Jacob. Loosely paraphrased, there are four parts to the covenant promise: 1) land, 2) offspring, 3) blessing, and 4) to be a blessing to all nations.
The fourth point is often called "the bottom line of the covenant." In other words, God's purpose in selecting Abraham, and through him, the children of Israel, was that the glory of God would be displayed to all nations and that they would be drawn to the worship of the One True God. That is Isaiah's point: "I will keep you and make you to be a covenant for the people and a light for the Gentiles" (Isa. 42:6b).
Unfortunately, Israel liked the first three parts of the covenant, because they were the recipients. But the bottom line did not seem to be such a great deal. That is why Jesus got so upset when a bazaar was set up in the part of the temple called, "the court of the Gentiles." He drove them all out saying, "Is it not written: 'My house will be called a house of prayer FOR ALL NATIONS'? But you have made it a 'den of robbers'" (Mark 11: 17).
Before we start pointing fingers at Israel, however, we in the church should take a long hard look at ourselves. Are we building the institution of the church for the purpose of blessing the world, or do we have a tendency to build it more like a fortress to hide in, hoping that Jesus comes back before the barbarians break through?
Jesus said, "The Son of Man came to seek and to save what was lost" (Luke 19: 10). What changes should we make to reorient ourselves towards fulfilling our primary mission, reaching a lost world with the good news of Jesus Christ and the kingdom of God?