"Who's There?"

A man knocked on a door.
"Who's there? asked God.
"Me," replied the man.
"Go away then," said God.
The man left and wandered in the arid desert until he realized his error and returned to the door. He knocked again.
"Who's there?" asked God.
"You," answered the man.
"Then come in," replied God. "There's no room here for two."

- Sufi teaching story