A shamelessly copied Ronnie Corbett joke:

A rural dean once went to visit one of his local priests. He could see the priest looked sad, so he asked what the matter was. The priest replied, “I have had my bicycle stolen, and what is worse, I think it has been stolen by one of my congregation.”

The wise rural dean thought for a second and said, “Ah, what you need to do.. is preach a sermon on the 10 Commandments. When you get to “Thou shalt not steal” look sternly at all the congregation. The person who looks embarrassed will be the one who stole it.”

A few weeks later, the rural dean visited the priest again and he was much happier. The priest told him he had got his bike back. The rural dean said, “Did you preach on the 10 Commandments?”

“Yes.” replied the priest

“And did you find out who took it?”

“Er, not exactly. When I got to “Thou shalt not commit adultery”, I remembered where I left it.”