Humaid (may Allah have mercy on him) says that Abu Al-Aliyah (may Allah have mercy on him) came to me along with one of my companions and said, "Both of you come with me to Bishr bin Asim, for you both are younger than me in age and have a better ability to remember hadith than I do." When we reached there, Abu Al-Aliyah said to Bishr, "Please narrate your hadith to these two." So Bishr said, "Uqbah bin Malik (may Allah be pleased with him) narrated this hadith to us: Once, the Prophet Muhammad (peace and blessings be upon him) sent out a detachment of the army. They attacked a certain people. A man from that people came out, and a man from the detachment rushed towards him with his sword drawn. The man said, 'I am a Muslim,' but the attacker did not pay attention to his words and struck him with the sword, killing him. News of this incident reached the Prophet Muhammad (peace and blessings be upon him), and he strongly condemned it in harsh words, which also reached the killer. Uqbah bin Malik (may Allah be pleased with him) says that while the Prophet Muhammad (peace and blessings be upon him) was delivering a sermon, the killer said, 'O Messenger of Allah! By Allah, he only said the kalimah to save his life.' The Prophet Muhammad (peace and blessings be upon him) turned away from him and from all those sitting on his side and continued his speech. This happened three times. Finally, the Prophet Muhammad (peace and blessings be upon him) turned towards him, and signs of grief and anger were visible on his blessed face, and he said, 'Allah Almighty has refused to accept my word regarding the one who kills a Muslim.'"