From Three Pieces of Advice, p. 132, Tales of the Dervishes by Idries Shah (Octagon Press, 1967): A man once caught a bird. The bird said to him, “I am no use to you as a captive. But let me free, and I will tell you three valuable pieces of advice.”
The bird promised to give the first piece of advice while still in the man’s grasp, the second when he reached a branch, the third after he gained the top of a mountain.
The man agreed, and asked for the first piece of advice.
The bird said: “If you lose something, even if it be valued by you as much as life itself - do not regret it.”
Now the man let the bird go, and it hopped to a branch.
It continued with the second piece of advice: “Never believe anything which is contrary to sense, without proof.”
Then the bird flew to the mountain-top. From here it said: “O unfortunate one! Within me are two huge jewels, and if you had only killed me they would have been yours!”
The man was anguished at the thought of what he had lost, but he said: “At least now tell me the third piece of advice.”
The bird replied: “What a fool you are, asking for more advice when you have not given thought to the first two pieces! I told you not to worry about what had been lost, and not to believe in something contrary to sense. Now you are doing both. You are believing something ridiculous and grieving because you have lost something! I am not big enough to have inside me huge jewels. You are a fool. Therefore you must stay within the usual restrictions imposed on man.”