The Ungrateful Son

By Jacob and Wilhelm Grimm

Once a man was sitting with his wife before their front door. They had a roasted chicken which they were about to eat together. Then the man saw that his aged father was approaching, and he hastily took the chicken and hid it, for he did not want to share it with him. The old man came, had a drink, and went away. Now the son wanted to put the roasted chicken back onto the table, but when he reached for it, it had turned into a large toad, which jumped into his face and sat there and never went away again. If anyone tried to remove it, it looked venomously at him as though it would jump into his face, so that no one dared to touch it. And the ungrateful son was forced to feed the toad every day, or else it would eat from his face. And thus he went to and fro in the world without rest.

The theme of The Ungrateful Son is implied because ____________________________.