Treasure

An old Chinese tale:

There was a man in China whose son had committed a crime and was very likely to be sent to prison. That was a great shame to the family and the night before the trial the father brought one of the family treasures, a very rare and big gem, to the judge. He told the judge: "This gem belongs to our family since many generations. It is a very rare and precious treasure. I want to give it to you." The old judge responded: "This is indeed a huge treasure. Your most precious treasure. My own most precious treasure it my integrity. So if I accept this gem, both of us will lose our most precious treasure."

What is our own most precious treasure?