There are two powerful effects that the gospel of grace has on a person who has been touched by it. First, the person who knows that he received mercy while an undeserving enemy of God will have a heart of love for even (and especially!) the most ungrateful and difficult persons. When a Christian sees prostitutes, alcoholics, prisoners, drug addicts, unwed mothers, the homeless, the refugees, he knows that he is looking in a mirror. Perhaps the Christian spent all of his life as a respectable middle-class person. No matter. He thinks: “Spiritually I was just like these people, though physically and socially I never was where they are now. They are outcasts. I was an outcast.
— Tim Keller, Ministries of Mercy, 60