In chapter 1 of 1st Peter the writer keeps moving from identity to responsibility, from calling to conduct, from privilege to obligation: God's part and our part. Peter sums it up in two words: "be holy." Why should the Bible have so much to say about holiness? The reasons are numerous, but they all come down to this finality: God is holy and the passion of His heart, held in vivid focus at Calvary, is the creation of a family of children who will be like Him. Readers of Dietrich Bonhoeffer's The Cost of Discipleship will remember his bold thesis that much of Christianity has subsided into a misunderstanding, and consequently a misuse of the concept of grace. The deviation is described in a sentence which he repeats many times:
"We have the doctrine of the justification of a sinner into the justification of the sin."
As a consequence, says Bonhoeffer, Christendom has been flooded and fouled with what he calls "cheap grace." This is the final resort of man justifying himself rather than penitently taking God's justification of him in Christ and the costly implications of the holy obedience to which it leads. God is not in the business of justifying sin. He is in the gracious business of justifying the sinner in order that the justified sinner may glorify him.