Every clergyman I know, myself included, has heard these words from a marginal congregant trying to justify his noninvolvement: “I may not be religious in the conventional sense, but I am a very spiritual person.” The implication is that being spiritual, following a religion solely of the heart and mind, is a purer, more authentic way of communing with God than the physical act of attending church, giving charity, or performing good deeds. I never had a satisfactory reply to that claim until my friend and colleague Rabbi David Wolpe of Los Angeles shared his answer with me. He would tell his spiritual congregant, “No, spirituality is what you feel, theology is what you believe, religion is what you do.” The most sublime religious faith becomes real only when it is translated into behavior, into doing things you might not otherwise do as an enactment of your religious faith.
— Harold S. Kushner, Nine Essential Things I’ve Learned About Life, p. 103-104.