3 guys and Jesus are near the Fountain of Forgiveness. Jesus says you can commit any sin you want as long as you drink from the fountain. They all shuffle off to commit various sins.
First one comes back and drinks. Jesus asks what he did. "I killed my wife." "You are forgiven."
Second one comes back and drinks. Jesus asks what he did. "I stole a TV." "You are forgiven."
The third one comes back and doesn't drink. Jesus asks why he didn't drink
"I pissed in the fountain."