Man: I want to borrow your donkey.
Nasreddin: I am sorry, but I have already lent it out.

[The donkey brayed; the sound came from Nasreddin's stable.]

Man: But I can hear the donkey, in there!
Nasreddin: A man who believes the word of a donkey in preference to my word does not deserve to be lent anything.

Idries Shah, The Pleasantries of the Incredible Mulla Nasrudin (1968)