What you do not want done to yourself, do not do to others. Confucius
If it is not right do not do it; if it is not true do not say it. Marcus Aurelius
I imagine that a hero is a man who does what he can. The others do not do it. Romain Rolland
Dine with a friend but do not do business with him. Armenian Proverb
Do not do evil - you will not be in eternal fear. Sumerian Proverb
Do not do all you can, do not spend all that you have, do not believe all that you hear, and do not tell all that you know. Chinese Proverb