The Once and Future King Book 3, Chapter 29
The next knight to come home is Lionel, Lancelot's cousin. He reports on his brother Bors, who is holy and pure (and annoying) like Galahad. Bors worries about what is morally right so much that he almost lets his brother be killed because he decides to save a more virtuous person instead. Lionel is at first furious that his brother could neglect his own brother for some "greater" cause, but then he begins to understand Bors's logic. He sees that Bors will find the Grail, because he is truly committed to being good. Arthur is fascinated.