Dietrich Bonhoeffer on Cheap Grace
Let the Christian rest content with his worldliness and with this renunciation of any higher standard than the world. He is living for the sake of the world rather than for the sake of grace. Let him be comforted and rest assured in his possession of this grace - for grace alone does everything. Instead of following Christ, let the Christian enjoy the consolations of his grace!
That is what we mean by cheap grace, the grace which amounts to the justification of sin without the justification of the repentant sinner who departs from sin and from whom sins departs.
Cheap grace is not the kind of forgiveness of sin which frees us from the toils of sin. Cheap grace is the grace we bestow on ourselves. Cheap grace is the preaching of forgiveness without requiring repentance, baptism without church discipline, Communion without confession, absolution without personal confession.
http://koti.mbnet.fi/amoira/blessings/gracech1.htm