Moral worth exists only when a man acts from a sense of duty
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

““a completely isolated metaphysic of morals, which is not mixed with any theology or physics or hyperphysics.” All moral concepts, he continues, have their seat and origin wholly a priori in the reason. Moral worth exists only when a man acts from a sense of duty; it is not enough that the act should be such as duty might have prescribed. The tradesman who is honest from self-interest, or the man who is kind from benevolent impulse, is not virtuous. The essence of morality is to be derived from the concept of law;” source