What did Prophet Muhammad (peace be upon him) say about the three cases in which a person may be lawfully killed in Islam?
 Narrated Abu Qilaba:                     That he was sitting behind `Umar bin `Abdul `Aziz and the people mentioned and mentioned (about at-Qasama) and they said (various things), and said that the Caliphs had permitted it. `Umar bin `Abdul `Aziz turned towards Abu Qilaba who was behind him and said. "What do you say, O `Abdullah bin Zaid?" or said, "What do you say, O Abu Qilaba?" Abu Qilaba said, "I do not know that killing a person is lawful in Islam except in three cases: a married person committing illegal sexual intercourse, one who has murdered somebody unlawfully, or one who wages war against Allah and His Apostle." 'Anbasa said, "Anas narrated to us such-and-such." Abu Qilaba said, "Anas narrated to me in this concern, saying, some people came to the Prophet and they spoke to him saying, 'The climate of this land does not suit us.' The Prophet said, 'These are camels belonging to us, and they are to be taken out to the pasture. So take them out and drink of their milk and urine.' So they took them and set out and drank of their urine and milk, and having recovered, they attacked the shepherd, killed him and drove away the camels.' Why should there be any delay in punishing them as they murdered (a person) and waged war against Allah and His Apostle and frightened Allah's Apostle ?" Anbasa said, "I testify the uniqueness of Allah!" Abu Qilaba said, "Do you suspect me?" 'Anbasa said, "No, Anas narrated that (Hadith) to us." Then 'Anbasa added, "O the people of such-and-such (country), you will remain in good state as long as Allah keeps this (man) and the like of this (man) amongst you."