From Luther, Bonhoeffer took a thoroughgoing emphasis on justification by faith (whose relationship to obedience he explored in his book Discipleship), as well as a theologia crucis (“theology of the cross”) which nurtured his conviction that God’s presence is paradoxically revealed in weakness and suffering. 

Luther’s centrality to Bonhoeffer’s thought is hardly surprising given Dietrich’s identity as a German Protestant who came of age during the Luther Renaissance of the 1920’s and studied under Holl, the leading Luther scholar of his generation (Stephen R. Haynes and Lori Brandt Hale, Bonhoeffer for Armchair Theologians, 8).