Since, according to the Talmud (Jewish Law), a Jewish wife is entitled to sexual pleasure, they decide to ask the rabbi.
The rabbi listens to to their story, strokes his beard and makes the following suggestion: "Hire a strapping young man. While the two are making love, have the young man wave a towel over you. That will help the wife fantasize and should bring on an orgasm."
They go home and follow the rabbi's advice. They hire a handsome young man and he waves the towel over them as they make love. But it doesn't help and she is still unsatisfied. Perplexed, they go back to the rabbi.
"Okay," says the rabbi, "let's try it reversed. Have the young man make love to your wife and you wave the towel over them."
The young man gets to work with great enthusiasm and the wife soon has an enormous, room shaking, screaming, orgasm.
The husband smiles, looks at the young man and says to him triumphantly, "you see, THAT'S the way to wave a towel!"