Nasreddin on the Day of Congregation
One Friday sometime in the 13th century in the Anatolian town of Akshehir, the Shaikh Nasreddin Hodja mounted the pulpit of the Grand Mosque and addressed the congregation. "O Believers," asked Nasreddin, "do you know what I am about to say?" "No, we don't," chorused the congregation. Nasreddin paused dramatically, then said: "If you don't know what I'm going to say, then what's the use of my talking?" And he descended from the pulpit. The congregation looked at one another in confusion.
A week went by, and when Friday came, Nasreddin once more climbed the steps of the pulpit and addressed the congregation. "O Believers, do you know what I am about to say?" This time the congregation was not going to be caught napping. "Yes," they all answered. "We know what you are about to say." Nasreddin again paused dramatically. Then he said, "Since you all know what I'm about to say, there's no need for me to say it." And he descended from the pulpit. The congregation was bewildered. Finally, they decided that next Friday, one half of them would answer "no" to the shaikh's question, and the other half would answer "yes."
A week went by, and when Friday came, the faithful hurried to the mosque. Nasreddin mounted the pulpit. "O Believers," he said, "do you know what I am about to say?" "No!" shouted half the congregation. "Yes!" shouted the other half. Nasreddin paused dramatically. Then he said, "Very good. Those of you who know tell those who don't." And he descended from the pulpit.
Taken from:
http://www.saudiaramcoworld.com/issue/197103/a.man.of.many.names.htm