This is a story told by Gertrud Staewen, as recounted in Victoria Barnett, For the Soul of the People: Protestant Protest against Hitler (Oxford, 1992), 22. The text below begins as a quote from Barnett, and then the extra indented part indicates that Barnett is quoting an interview with Staewen. This encounter occurred in the 1920s:
One New Year’s Eve, Staewen attended a gathering of religious socialists. By temperament a devil’s advocate, she had trouble remaining quiet at such meetings. One part of her longed for the intellectual community they offered; another part of her poked fun at the pretensions so often displayed. So it was on this evening. People stood up and expounded their theories or read poems or selections of novels they had written, as Staewen recalled ironically,
to promote socialism and improve human beings. A great deal of totally idealistic rubbish that wasn’t true was read aloud to make us all more Christian and more socialist.The man was the Swiss theologian Karl Barth. After the meeting ended in the early hours of the morning, he drew Staewen into a deep conversation. Barth and his friend Thurneysen, a practical theologian, would lead a large group of young Germans into the church opposition to Hitler.
Finally I jumped up and got angry, and said that no novel had ever led a person to Christ unless it was by Dostoevski. For him I’d make an exception. Now, besides us, there were several men toward the back whom we didn’t know. They were smoking dreadfully. As I spoke about Dostoevski, the curtain of smoke opened and a man stood up. At that time he was still quite young; he looked like a woodcut of a Swiss farmer. He asked me, “Do you know my friend Eduard Thurneysen?” I said, No, I didn’t. Then he said, “Read him!”