What is compassion

Buddha was the most compassionate being that the earth could produce.One of the stories which gives us a glimpse of his nature is given below:
Once there was a man who came and spat on Buddha.His disciples were angered at this behaviour.Buddha wiped his face and said to the man,"Thank you sir.You created a context in which I could see whether I can still be angry or not.And I am not and I am tremendously happy.And you created a context for Ananda to see his anger.Many thanks,we are so grateful.Once in while please,you are invited to come.Whenever you have an urge to spit you can do it on us.

The man was shocked, he could not sleep whole night.He felt the way Buddha was grateful.The "Thank you" came from his heart directly it was not a formality.The next day he went to Buddha to ask for forgiveness.Buddha was seated near the Ganges.He showed the man the river how everything was flowing.Twenty four hours you are carrying it.Forget all about it.I cannot forgive you because I was not angry with you.If I was angry I would have forgiven.Go fall on the feet of Ananda he will be happy.

Our reactions to a particular action is the measure of our compassion.