A man wonders if having sex on the Sabbath is a sin because he is not sure if sex is work or play. So he goes to a priest and asks for his opinion on this question.
After consulting the Bible, the priest says, "My son, after an exhaustive search, I am positive that sex is work and is therefore not permitted on Sundays".
The man thinks: "What does a priest know about sex"? So he goes to a Lutheran minister, who after all is a married man and experienced in this matter.
He queries the minister and receives the same reply: "Sex is work and therefore not for the Sabbath"!
Not pleased with the reply, he seeks out a Rabbi, a man of thousands of years tradition and knowledge.
The Rabbi ponders the question, then states, "My son, sex is definitely play".
The man replies, "Rabbi, how can you be so sure when so many others tell me sex is work"?
The Rabbi softly speaks, "My son, if sex was work, my wife would have the maid do it".
Now that was really funny.
While having sex with porn star Kasey Grant I asked how she feels about getting fucked in front of cameras. She said it is play having sex and work when I get paid.
The version of this joke I enjoy is in a military setting:
One morning, Army officers gathered for a meeting with the colonel. He was a 1/2 hour late, and arrived to find the others waiting. "Good morning gentlemen. Sorry for being late. Last night the wife and I engaged in sex several times
and this morning I'm feel tired. I love sex, but this makes me wonder if it's mostly pleasure or mostly work." "Major, what percent of sex would you say is pleasure and how much is work?" He replied, "sir, I'd say sex is 5% pleasure and 95% work". Next the colonel asked the captain. He replied, "sir, I'd say sex is 50% pleasure and 50% work". Then the colonel asked the lieutenant. He replied, "sir, I'd say sex is 95% pleasure and 5% work". Just then the colonel's aide, a corporal came in with coffee for the officers. The colonel decided to get his input. "Corporal, what percent of sex would you say is work, and what percent is pleasure?" The corporal replied, "sir, I'd say sex is 100% pleasure and 0% work." Puzzled, the colonel asked him why. The corporal replied, " 'cuz if there were any work to it at all, you guys would have me doing it for you."
Sex isn’t Work, Sex isn’t Fun,
Sex is a Health&Happy,
so let’s do it everyday and people would be happy&healthy worldwide 
