( saying ) the reward for acting in a moral or correct way is the knowledge that you have done so, and you should not expect more than this, for example praise from other people or payment
VIRTUE IS ITS OWN REWARD
Meaning of VIRTUE IS ITS OWN REWARD in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005