Nasruddin Say:"Let the half who know what I am going to say, tell it to the half who don't,"
Once Nasreddin was invited to deliver a sermon. When he got on the pulpit, he asked, Do you know what I am going to say? The audience replied "no", so he announced, I have no desire to speak to people who don't even know what I will be talking about! and left.
The people felt embarrassed and called him back again the next day. This time, when he asked the same question, the people replied yes. So Nasreddin said, Well, since you already know what I am going to say, I won't waste any more of your time! and left.
Now the people were really perplexed. They decided to try one more time and once again invited the Mulla to speak the following week. Once again he asked the same question – Do you know what I am going to say? Now the people were prepared and so half of them answered "yes" while the other half replied "no". So Nasreddin said Let the half who know what I am going to say, tell it to the half who don't, and left.