In a small village lived a washerman named Suddhapata. He had a donkey that was very weak because he did not feed the animal regularly. One day, the washerman found the dead body of a tiger while he was collecting wood from the forest. Suddhapata was very happy and thought, "I am lucky. I can skin the animal and cover my donkey with that skin and drive it into wheat farms where he will have plenty to graze. Thinking that he is a tiger, people will keep away from him. This way, my donkey will have plenty of food."

He acted on his plan and the donkey would go to the wheat farm every evening, have his day’s fill and return to his master’s house in the morning. This went on for sometime. The donkey became so strong and sturdy that it became difficult for the washerman to pull him to the peg and tie him to it.

One day, when he was happily grazing at the wheat farm, the donkey heard the voice of a female donkey and began to respond to it in ecstasy. Then the watchman and others at the farm at once recognised him as a donkey in a tiger skin and killed him.

Moral
One should not open his mouth, when he should not.

Or

Don’t try to be what you are not.