“First, Christians are called upon to love all men as neighbors, loving them as ourselves. Second, we are to love all true Christian brothers in a way that the world may observe.
This means showing love to our brothers in the midst of our differences– great or small– loving our brothers when it costs us something, loving them even under times of tremendous emotional tension, loving them in a way the world can see.
In short, we are to practice and exhibit the holiness of God and the love of God, for without this we grieve the Holy Spirit.
Love– and the unity it attests to– is the mark Christ gave Christians to wear before the world. Only with this mark may the world know that Christians are indeed Christians and that Jesus was sent by the Father.” (John 13:34-35; 17:21)
–Francis Schaeffer, The Mark of the Christian in The Complete Works of Francis A. Schaeffer: A Christian Worldview, Volume Four, A Christian View of the Church (Wheaton, IL: Crossway, 1982), 204.