"Morality is Temporary, Wisdom is Permanent."
The quote lies in a book called Kingdom of Fear: Loathsome Secrets of a Star-Crossed Child In the Final Days of the American Century, penned by Thompson and published in 2003. The quote was in a response to a story he tells about how when he was 9, he and his friends tipped over a mailbox in front of a bus (the driver of which was especially cruel to him and his friends). Tampering with mail, of course, is a federal offense, and it brought two Federal Agents to his door. They began questioning him, accusing him of the deed, and saying that all his friends had ratted on him. However, he had the gall to question them on this, and when they weren't able to prove they had gotten any confessions or witnesses, they left.
This piece replaces the now-unavailable Lois McMaster Bujold piece that was originally part of the 20 initial Who Said What pieces. It was later discovered that the Bujold quote was misattributed, and all copies were destroyed.
A timelapse video showing the creation of this piece can be seen here: