Both piety and wisdom involve self-command, self-conquest, self-denial, strength of will, and firmness of purpose. But though these qualities are instrumental in the pursuit of piety, they are not its nature. It is the regard for the transcendent, the devotion to God, that constitute its essence.
— Abraham Joshua Heschel, Moral Grandeur and Spiritual Audacity by Abraham Joshua Heschel, Susannah Heschel, editor