For you are a people holy to the Lord your God. The Lord your God has chosen you to be a people for his treasured possession, out of all the peoples who are on the face of the earth.
God's love chooses people and calls them to be His holy people. This principle was most vividly pictured in the Old Testament where Israel is God's treasured possession, uniquely called into covenant with Him to show the world the power and love of the Lord. That is a powerful privilege and one that the whole history of Israel is showing us even today.
Christians should learn from the way God treasures Israel in the Old Testament and notice how He calls them to obey Him in holiness. We too are His treasured possessions in Christ (see 1 Peter 2:9). Christians are a chosen race, a royal priesthood, a people for God's own possession so that we might proclaim the glory of the God Who has called us to Himself. It is a particular kind of relationship of powerful privilege.
This does not mean that Christians are to act like stuck up religious snobs. That did not work as an evangelistic strategy for Israel and it won't work for us. We are in a unique position belonging to God so that we might do one thing clearly: display God and His glorious salvation in Christ to the world. God put us in the world so that His glory would be accessible in the church. We are holy displays of God's great love in Christ. Want to see what Jesus can do? Look at His church, His prized possession bought at the cost of His blood, the people He set to priestly minister His saving work to the world. There is nothing more special or important than that!