The Wolf and the Crane
A Wolf, after too greedily devouring his prey, happened to have a bone stick in his throat, which gave him so much pain that he went howling up and down, and importuning every creature he met to lend him a kind hand in order to his relief; nay, he even promised a reward to anyone who should undertake the operation with success. At last the Crane, tempted with the lucre of the reward, and having first made the Wolf confirm his promise with an oath, undertook the business, and ventured his long neck into the rapacious felon's throat.
In short, he plucked out the bone, and expected the promised gratuity; when the Wolf, turning his eyes disdainfully towards him, said, "I did not think you had been so unreasonable! Have I not suffered you safely to draw your neck out of my jaws? And have you the conscience to demand a further reward?"
When we do good to bad men, we must not expect good from them.