It is narrated from Hasan Basri that he said: During the days of the Battle of Jamal, a man came to Hazrat Zubair and said, "Shall I kill Ali (may Allah be pleased with him) for you?" He replied, "How?" The man said, "I will go to him and tell him that I am with him, then, taking advantage of the opportunity, I will kill him deceitfully." Hazrat Zubair said, "No. I heard the Messenger of Allah (peace and blessings be upon him) say that faith prevents killing by deceit. A believer should not be killed deceitfully."