What is your favorite fable or parable that teaches a moral theme or lesson?

For example from Charlie Wilson’s war:

Gust: Did I ever tell you the story of the Zen master and the little boy? On his 16th birthday, a boy gets a horse as a present. All the villagers say, “How wonderful!” The Zen master says, “We’ll see.” One day, the boy is thrown from the horse and is hurt and can no longer walk. All the villagers say, “How terrible!” The Zen master says, “We’ll see.” A short time later, war begins, and all the young men of the village are taken away to be soldiers, but this boy can’t fight, so he is spared, and all the villagers say, “How wonderful!”
Charlie: And the Zen master says, “We’ll see…”
Gust: You’re catching on…