You will be surprised to know that Mahavira is the only man in the whole of history who has said, "Don't say anything which you would not like to be associated with you forever, because whatsoever you say is going to be eternal." He is the only man, but what he is saying certainly has a tremendous insight. His reason for not saying bad words, ugly words, is very scientific, not religious. He is saying it because those words will remain always; they will be your footprints in time. Don't leave anything ugly behind you.

From Ignorance to Innocence
Chapter #24