The people knew that Mulla Nasruddin was generally intolerant of preachers and lecturers, so they asked him to give a sermon. He climbed into the pulpit and said: “Do you know what I am going to speak about?”
“No,” everybody answered.
“If you are so ignorant, I am not going to waste time speaking to you,” Nasruddin said and climbed down from the pulpit.
The following day he put the same question to them. This time everyone’s answer was, “Yes, we know.”
“If you know,” Nasruddin replied, “then what am I here for?” And he left the mosque.
The third day, to the same question, half of the worshipers said, “We know,” while the other half said, “We don’t know.”
So Nasruddin responded: “Let those who know tell those who don’t.”