Buddha's advice to Rahula
Being a young boy, Rahula(Rahul) often told lies for fun. The Buddha decided to teach him the importance
of truthfulness.
On one occassion, the showed Rahula a vessel with a small amount of water in it and said, "A person who is not ashamed of telling lies knowingly, has little virtue in him. He is just like this vessel which has but a small amount of water in it."
Next, He threw away the water from the vessel and said, "A person who is not ashamed of telling lies knowingly, throws away his virtue just like this water being thrown away."
Then, the Buddha turned the vessel right way up and said, "A person who is not ashamed of continuously telling lies knowingly, is as hollow and empty as this vessel."
The Buddha also used another example to show him how to cultivate good conduct.
"What do you think of a mirror? What is its purpose?" the Buddha asked Rahula.
"It is meant to reflect one's appearance," he answered.
"In the same way, one's actions, words and thoughts must be reflected upon as if one were looking at them in a mirror. Before actions are done, consider whether they are harmful to yourself, to others or to both yourself and others. Only when they are beneficial to all should they be done. In the same way, before you speak, consider whether your words are harmful to yourself, to others or to both yourself and others. Only if they are beneficial to all should they be spoken. When thoughts arise, consider whether they are harmful to yourself or to others or to both yourself and others. If they are not beneficial to all, they should be discarded. This is the way you must train yourself to consider your actions, words and thoughts. This is the way to purify yourself."
Rahula was delighted by the words of the Buddha and decided to discipline himself to become a good monk.