Dietrich Bonhoeffer (1906 – 1945) was a German Lutheran pastor, theologian, anti-Nazi dissident, and key founding member of the Confessing Church. Apart from his theological writings, Bonhoeffer was known for his resistance to Nazi dictatorship. He was arrested in April 1943 by the Gestapo and imprisoned at Tegel prison. Later he was transferred to a Nazi concentration camp. After being associated with the plot to assassinate Adolf Hitler, he was quickly tried and executed by hanging on 9 April 1945 as the Nazi regime was collapsing.
Shortly before his death, Bonhoeffer started writing on what he called "Religionless Christianity". These writings became influential in the development of a post-theistic theology grounded in the work of liberation. The following are some excerpts. I've also included a document that holds all the relevant material for those who would like to do further research.