Mullah Nasruddin went on a pilgrimage to Mecca, and on the way he passed through Medina.
As he was walking by the main mosque there, a rather confused looking tourist approached him. "Excuse me sir," said the tourist, "but you look like a native of these parts; can you tell me something about this mosque? It looks very old and important, but I've lost my guidebook."
Nasruddin, being too proud to admit that he, too, had no idea what it was, immediately began an enthusiastic explanation. "This is indeed a very old and special mosque." he declared, "It was built by Alexander the Great to commemorate his conquest of Arabia."
The tourist was suitably impressed, but presently a look of doubt crossed his face. "But how can that be?" he asked, "I'm sure that Alexander was a Greek or something, not a Muslim. . . Wasn't he?"
"I can see that you know something of these matters." replied Nasruddin with chagrin, "In fact, Alexander was so impressed at his good fortune in war that he converted to Islam in order to show his gratitude to God."
"Oh, wow." said the tourist, then paused. "Hey, but surely there was no such thing as Islam in Alexander's time?"
"An excellent point! It is truly gratifying to meet a visitor who understands our history so well," answered Nasruddin. "As a matter of fact, he was so overwhelmed by the generosity God had shown him that as soon as the fighting was over he began a new religion, and became the founder of Islam."
The tourist looked at the mosque with new respect, but before Nasruddin could quietly slip into the passing crowd, another problem occurred to him.
"But wasn't the founder of Islam named Mohammed? I mean, that's what I read in a book; at least I'm sure it wasn't Alexander."
"I can see that you are a scholar of some learning," said Nasruddin, "I was just getting to that. Alexander felt that he could properly dedicate himself to his new life as a prophet only by adopting a new identity. So, he gave up his old name and for the rest of his life called himself Mohammed."
"Really?" wondered the tourist, "That's amazing! But...but I thought that Alexander the Great lived a long time before Mohammed? Is that right?"
"Certainly not!" answered the Mullah, "You're thinking of a different Alexander the Great. I'm talking about the one named Mohammed."