Jack goes to his friend Mike and says, "I'm sleeping with the minister's wife so
can you please keep him back in church for an hour after the service, for me?"

Mike doesn't like it, but being a friend, he agrees.
After the service, Mike starts talking to the minister, asking him all sorts of
silly unrelated questions, just to keep him occupied.
The minister eventually gets annoyed and asks Mike, " What are you up to?"

Mike, feeling guilty, finally confesses to the minister,
"Well my friend is sleeping with your wife right now so he asked me to keep you
occupied."

The minister thinks for a minute, smiles, puts a brotherly hand on Mike’s
shoulder and says, “You better hurry home now. My wife died a year ago.”

and then

When I was young I decided I wanted to be a doctor, so I took the entrance exam to go to Medical School.
One of the questions asked us was to rearrange the letters PNEIS into the name of an important human body part which is most useful when erect. Those who answered spine are doctors today. The rest of us are sending jokes via email.