From Bonhoeffer's Cost of Discipleship: Cheap Grace

“Cheap grace is the grace we bestow on ourselves… the preaching of forgiveness without repentance, baptism without church discipline, communion without confession. Cheap grace is grace without discipleship…
Costly grace is the treasure hidden in the field; for the sake of it a man will gladly go and sell all that he has. It is the pearl of great price to buy which the merchant will sell all his goods. It is the kingly rule of Christ…
Costly grace is the gospel which must be sought again and again, the gift which must be asked for, the door at which a man must knock…
Such grace is costly because it calls us to follow, and it is grace because it calls us to follow Jesus Christ. It is costly because it costs a man his life, and it is grace because it gives a man to only true life. Costly grace is the incarnation of God…”

“It is a fatal misunderstanding to suppose that it was the great discovery of the Reformation that God’s forgiving grace automatically conferred upon the world both righteousness and holiness.”

“Luther had taught that man cannot stand before God, however religious his works and ways may be, because at bottom he is always seeking his own interests. In the depth of his misery, Luther had grasped by faith the free and unconditional forgiveness of all his sins. That experience taught him that this grace had cost him his very life, and must continue to cost him the same price day by day.”

“At the end of a life spent in the pursuit of knowledge Faust has to confess: ‘I now do see that we can nothing know.’ That is the answer to a sum, it is the outcome of a long experience. But as Kierkegaard observed, it is quite a different thing when a freshman comes up to the university and uses the same sentiment to justify his indolence. As the answer to a sum it is perfectly true, but as the initial data it is a piece of self-deception. For acquired knowledge cannot be divorced from the existence in which it is acquired. The only man who has the right to say that he is justified by grace alone is the man who has left all to follow Christ. Such a man knows that the call to discipleship is a gift of grace, and that the call is inseparable from the grace. But those who try to use this grace as a dispensation from following Christ are simply deceiving themselves.”

“Happy are the simple followers of Jesus Christ who have been overcome by his grace, and are able to sing the praises of the all-sufficient grace of Christ with humbleness of heart. Happy are they who, knowing that grace, can live in the world without being of it , who, by following Jesus Christ, are so assured of their heavenly citizenship that they are truly free to live their lives in this world. (That’s where I want to be.) Happy are they who know that discipleship simply means the life which springs from grace, and that grace simply means discipleship. Happy are they who have become Christians in this sense of the word. For them the word of grace has proved a fount of mercy.”