Aesop’s Fables: The Wolf & the Crane.
Esoph Sables. The Wolf and the crane
If you pull that bone out for me. The crane, as you can imagine, was very uneasy about putting her head in a Wolf's throat, but she was grasping in nature, so she did what the Wolf asked her to do. When the Wolf felt that the bone was gone, he started to walk away. But what about my reward? Called the crane anxiously. What, snarled the Wolf whirling around. Haven't you got it?
The moral of the story is expect no reward for serving the wicked