From his faith the breathe of vision came which enabled him to separate the gold in life from the dross and to differentiate  what was not essential in the life of man. From it came the constancy of mind, persistency of purpose, love of suffering humanity and of truth, justice and goodness. But it was not enough for him to seek justice, truth, honesty and goodness for their own sake and patiently to suffer for them. No, according to Bonhoeffer, we have to do so in loyal obedience to Him who is the source and spring of all goodness, justice and truth and on whom he felt absolutely dependent.  

Memoir by G. Leibholz in  Dietrich BonhoefferThe Cost of Discipleship1961 edition, 22.