This incidence that happened in Gautama Buddha's life has a great lesson for all.
On a certain day, everybody came and bowed down to Buddha but one man came and spat on his face. Anandatheerta, Buddha's close disciple who adored and worshiped him, lost his temper because of the act.
He said, "Give me permission and I will teach this man a lesson. How could he spit on your face?"
Gautama said, "No," and thanked that man.
He said, "Thank you very much for spitting on my face because this has given me an opportunity to see whether I am still capable of anger or not. I am very happy to know that I am not angry even if people spit on my face. That is very good. You helped me evaluate myself, and at the same time, you have also given Ananda that opportunity. So thank you very much. You have made both of us realize where we are right now."