Ask a fox for its skin.

  

"Long ago, there lived a young man, called Lisheng, who had just married a beauty. The bride was very willful. One day, she had an idea that a coat of fox fur would look pretty on her. So she asked her husband to get her one. But the coat was rare and too expensive. The helpless husband was forced to walk around on the hillside. Just at the moment, a fox was walking by. He lost no time to catch it by the tail. 'Well, dear fox, let's make an agreement. Could you offer me a sheet of your skin? That isn't a big deal, is it?'

"The fox was shocked at the request, but she replied calmly, 'Well, my dear, that's easy. But let my tail go so that I can pull off the skin for you.' So the delighted man let her free and waited for the skin. But the moment the fox got free, she ran away as quickly as she could into the forest."

The story can be used to illustrate that it is hard to ask someone to act against his own will, even in a seemingly negligible manner.