From Robert Sagers:
Pastor-theologian Tim Keller on the relationship between the church and the kingdom:
What is the relationship of the church to the kingdom? On the one hand, the church is a “pilot plant” of the kingdom of God. It is not simply a collection of individuals who are forgiven. It is a “royal nation” (1 Peter 2:9), in other words, a counterculture. The church is to be a new society in which the world can see what family dynamics, business practices, race relations, and all of life can be under the kingship of Jesus Christ. God is out to heal all the effects of sin: psychological, social, and physical.
On the other hand, the church is to be an agent of the kingdom. It is not only to model the healing of God’s rule but it is to spread it. “You are . . . a royal priesthood, a holy nation . . . that you may declare the praises of him who called you out of darkness into his wonderful light” (1 Peter 2:9). Christians go into the world as witnesses of the kingdom (Acts 1:6-8). To spread the kingdom of God is more than simply winning people to Christ. It is also working for the healing of persons, families, relationships, and nations; it is doing deeds of mercy and seeking justice. It is ordering lives and relationships and institutions and communities according to God’s authority to bring in the blessedness of the kingdom.
—Timothy J. Keller, Ministries of Mercy: The Call of the Jericho Road, 2nd ed. (Phillipsburg, NJ: P&R), 54.