Cicero, Tusculan Disputations 2.17

Never value anything as profitable to thyself which shall compel thee to break thy promise, to lose thy self-respect, to hate any man, to suspect, to curse, to act the hypocrite, to desire anything which needs walls and curtains.

Wilt thou, then, my soul, never be good and simple and one and naked, more manifest than the body which surrounds thee?

If it is not right, do not do it; if it is not true, do not say it.