Nasruddin went to the bathhouse.
When the attendant saw Nasruddin's shabby clothes, he treated him poorly, giving him a threadbare towel and only a tiny piece of soap. Nevertheless, after Nasruddin finished his bath, he tipped the attendant very generously.
On his next visit, the attendant greeted Nasruddin with great respect, remembering the generous tip. He gave Nasruddin several luxurious towels and a new bar of soap. But when he left, Nasruddin gave the attendant no tip at all.
"That's for last time," Nasruddin explained, "and the tip I gave you last time was for this time. Now we're even!"
Inspired by: 202 Jokes of Nasreddin Hodja by Her Hakki Mahfuzdur
Notes: This is story 58 in the book. You can learn more about Turkish baths at Wikipedia.