Musannaf Ibn Abi Shayba 28:580

Shababa ibn Sawwar narrated to us, he said: Sulayman ibn al-Mughira narrated to us, from Humayd ibn Hilal, who said: Abu al-Aliyah came to me and to a companion of mine and said: "Come, for you two are younger than me and more retentive of hadith than me." He said: So we set off until we came to Bishr ibn Asim al-Laythi. Abu al-Aliyah said: "Narrate to these two your hadith." He said: Uqbah ibn Malik al-Laythi narrated to me, he said: The Prophet, may Allah bless him and grant him peace, sent a military detachment, and it raided a people. A man from the people fled, and a man from the detachment followed him, and with him was a drawn sword. The fleeing man from the people said: "I am a Muslim." But he did not look into what he said, so he struck him and killed him. The news reached the Prophet, may Allah bless him and grant him peace, and the Prophet, may Allah bless him and grant him peace, said a harsh statement. It reached the killer. While the Prophet, may Allah bless him and grant him peace, was delivering a sermon, the killer said: "By Allah, O Prophet of Allah, he did not say what he said except to seek refuge from being killed." The Prophet, may Allah bless him and grant him peace, turned away from him and from those of the people who were next to him. He did that twice, and each time the Prophet, may Allah bless him and grant him peace, turned away from him. He could not bear it, so he said the same thing a third time. The Prophet, may Allah bless him and grant him peace, turned his face toward him, and you could recognize the displeasure on his face. He said: "Indeed, Allah has refused for me [to accept the excuse of] one who kills a believer," saying that three times.