Sa’d bin Abi Waqas (may Allah be pleased with him) one day heard a man grumpling; when he listened closely to what he was saying he realized he was abusing Ali, Talhah and Zubair (may Allah be pleased with them). He told him to stop, but he would not listen and continued. Finally, Saad bin Abi Waqas (may Allah be pleased with him) lost his temper, and said if he did not control his tongue he would put a curse on him. Arrogantly the man told him that he was arrogating powers to himself and he asked him if he thought he was a Prophet..
Listening to the man’s bitter words, he merely turned away. He went, made his ablutions for prayer and offered two supererogatory units of prayer. Then he entreated Allah Almighty:
“Oh Allah you know that this man is abusing men of purity, with whom You Yourself are Pleased because of their goodness. Surely You will not approve of theses abuses. May this man be a lesson for such other men.”
He had barely done with his supplications when people saw that a raging she-camel had broken away from the rope which tethered her, and leaving her home had entered in the midst of a crowd of people. It seemed as if she was looking for a particular person. In seconds she had the head of a person in her bloodthirsty jaws and was shaking it violently from side to side. Finally his neck broke and in no time he had become the prey of death. People were stunned in silence. The dead man was non other than the one who had been abusing the noble companion a few minutes earlier, and against whom Saad bin Abi Waqas (may Allah be pleased with him) appeared. He had indeed become a lesson for people.
From Commanders of The Muslim Army By Mahmood Ahmad Ghandanfar