Anger always harms oneself immediately,
even if never expressed to harm others later.
On another occasion, Rahula followed his teacher, Sariputra, on a trip to teach the Dharma. At noon, they begged for alms in the vicinity of Rajagriha. They met a young hooligan, who poured sand on purpose into Sariputra’s alms-bowl, and hot Rahula’s head with a stick. Blood kept flowing out from the injured part of Rahula’s head.
Sariputra comforted Rahula, saying, “Rahula, as disciples of the Buddha, we must cultivate the virtue of patience. We must not be angry with evil people. On the other hand, we should even pity them, because they do not know that every action will produce results, so they commit evil actions.” [Ed: Which is why we should do our best to help them realise their mistakes.]
After listening to Sariputra, Rahula was calm and unruffled. Without uttering a word, he went to the riverbank by himself, and washed away the blood on his head and face. Then, he used his handkerchief to dress the wound. He then continued to beg for alms from others, as if he had not been injured at all.
The Ten Great Disciples
Lin Shi Min