The Countryman and the Snake

by Aesop

A VILLAGER found a Snake under a hedge, almost dead with cold. He could not help having compassion for the poor creature, so he brought it home, and laid it upon the hearth near the fire; but it had not lain there long, before (being revived with heat) it began to erect itself, and fly at his wife and children. The Countryman, hearing an outcry, and perceiving what the matter was, caught up a mattock, and soon dispatched him, upbraiding him at the same time in these words: Is this, vile wretch, the reward you make to him that saved your life?

Moral:
Kindness to the ungrateful and the vicious is thrown away.