“Once upon a time, a poor widow sends her young son Hans into the village to fetch a simple meal, and along the way into town he discovers a lump of gold. Thrilled, he heads back home to show his mother his amazing good luck. But no sooner has he started back than he meets a knight who persuades him to exchange the gold for the knight’s steed. “The better for plowing!” the knight assures the boy. Further down the way, a farmer explains that the widow can’t eat a horse, so why not exchange the horse for the farmer’s cow? After making this seemingly reasonable bargain, the boy continues home but then meets up with a neighbor carrying a goose under his arm. Of course the widow wants a meal today, says the neighbor, so why not exchange cow for goose? Done. Finally, nearly home, he meets up with a boy who tells him that if he exchanges the goose for a whetstone he can keep his knife sharpened for slaughtering any number of geese in the future. Done again. But when he gets home he notices the clumsy stone in his pocket and, puzzled at its presence, throws it away before crossing the threshold of his home, none the sadder and certainly none the wiser.” — Reconciling Judas: Evangelizing the Theologians, by Edward T. Oakes; seen here.
This seems to have been (very usefully) adapted from Hans in Luck, in Grimm’s Fairy Tales.