There was once a rabbi who was revered by the people as a man of God. Not a day went by when a crowd of people wasn't standing at this door seeking advice or healing or the holy man's blessing. And each time the rabbi spoke, the people would hang on his lips, drinking in his every word.
There was, however, in the audience a disagreeable fellow who never missed a chance to contradict the master. He would observe the rabbi's weaknesses and make fun of his defects to the dismay of the disciples, who began to look on him as the devil incarnate.
Well, one day the "devil" took ill and died. Everyone heaved a sigh of relief. Outwardly they looked appropriately solemn but in their hearts they were glad for no longer would the master's inspiring talks be interrupted or his behavior criticized by this disrespectful heretic.
So the people were surprised to see the master plunged in genuine grief at the funeral. When asked by a disciple later if he was mourning over the eternal fate of the dead man, he said, "No, no. Why would I mourn over our friend who is now in heaven? It was for myself I was grieving. That man was the only friend I had. Here I am surrounded by people who revere me. He was the only one who challenged me. I fear that with him gone, I shall stop growing." And as he said these words, the master burst into tears.