Melampus

Melampus' ears were licked by snakes, and after he could hear what animals said. One day he was taken prisoner, and he heard the woodworms in the timber of his cell saying that the house would soon collapse. He warned his captors of this, and they escaped. After that they always held him in high honor.

I suppose that the moral of this story is that if you help someone they'll help you. That' what they always say in movies when they're blackmailing someone, "Help me and I'll help you." Except here he did it of his own free will, and because of this they like him better because he helped them despite being their prisoner.