Uncle Ajax prided himself on his memory. He always knew where he put down his glasses, and he never seemed to forget which box held his old watches and ties. Nonetheless, one morning he discovered that his expensive new hat was not on the hat rack by the front door. He couldn't remember where he had worn it last, and he hadn't gone anywhere without it. His wife didn't know anything about it, and that lost hat really aggravated him.
He spent days looking for it.
Finally, he accepted the fact that the hat was gone forever, and, since he was also something of a cheat, decided that he'd go to the nearby church on Sunday morning, where there would be a lot of men showing up in their best clothes including, of course, fine hats. He would come in a little late and sit at the back. Then, during the service, he would sneak out and grab a hat from the rack at the front door.
On Sunday, he went to the church and sat at the back. The sermon was about the 10 Commandments. He sat through the whole sermon. The sermon had apparently really reached him, because, instead of sneaking out and stealing one of the parishioners' hats, he stayed behind as everyone else left the building, and went up to the pulpit to talk to the minister.
He said to the minister "Father, I have to admit that I came here today to steal a hat to replace the one I lost. But after hearing your sermon on the 10 Commandments, I changed my mind".
The minister was visibly pleased, having served in that parish for 20 years without a single member complimenting him on anything he had ever said. "Bless you, my son" he burbled. "Was it when I started to preach 'thou shall not steal' that changed your heart?"
My uncle responded "No, it was the one on adultery. When you started to preach about that, I remembered where I left my hat".