Karl Barth's first sermon in the penitentiary of his native Basel was on August 1, 1954, and his last on March 29, 1964, when he ended his preaching activity for health reasons. During these years he preached there 28 times. The texts of those sermons were collected in two volumes: Den Gefangenen Befreiung [Aἰχμαλοτοις ἄφεσιν] (1959) and Rufe mich an! [Call Me!] (1965).

Writing about his experience in the Basel penitentiary, Barthes observed that "everything was somehow more real than in an ordinary Church with the ordinary Christians gathered there." It is no coincidence, apparently, that Bart chose to celebrate his seventieth birthday in prison, with a liturgical service and sermon.

The Swiss theologian wants to build a meaningful intimacy with the prisoners. He refers to the situation of the prisoners, but with due discretion and away from any atmosphere of didacticism and condescension from an allegedly privileged position. He wants to be perceived as one of them, which is why there is no lack of references to his life and activities, which are usually done with his characteristic humor.