Dietrich Bonhoeffer's writings are among those that I return to again and again. I do not always agree with him, but I almost never read him without benefit.
In a couple of weeks I'll be preaching revival services at my brother David's church on the theme, "Christ and His Church." This theme brought to mind a comment I saw attributed to Bonhoeffer. I've just located it in vol.10 of Dietrich Bonhoeffer Works. It's from a sermon he preached on July 29, 1928, while serving as a pastor in Barcelona.
I think Bonhoeffer is correct here, both in his observation and the urgency of his appeal to reconsider the meaning of "church." Check it out.