Be not one whose motive for action is the hope of reward.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

“So the man is praised, who, having subdued all his passions, performeth with his active faculties all the functions of life, unconcerned about the event.” “Let the motive be in the deed and not in the event. Be not one whose motive for action is the hope of reward. Let not thy life be spent in inaction.” “For the man who doeth that which he hath to do, without affection, obtaineth the Supreme.” “He who may behold, as it were inaction in action, and action in inaction, is wise amongst mankind.” source