Ideally, however, the church itself is not made up of natural “friends.” It is made up of natural enemies. What binds us together is not common education, common race, common income levels, common politics, common nationality, common accents, common jobs, or anything of the sort. Christians come together, not because they form a natural collocation, but because they have been saved by Jesus Christ and owe him a common allegiance. In the light of this common allegiance, in light of the fact that they have all been loved by Jesus himself, they commit themselves to doing what he says – and he commands them to love one another. In this light, they are a band of natural enemies who love one another for Jesus’ sake.
D.A. Carson, Love in Hard Places
June 16, 2010