سنن ابن ماجه

It was narrated from Abu Umamah bin Sahl bin Hunaif that: `Uthman bin 'Affan looked at them when they spoke of killing. He said: “Are they threatening to kill me? Why would they kill me? I heard the Messenger of Allah (ﷺ) say: “It is not lawful to shed the blood of a Muslim except in one of three (cases): a man who commits adultery when he is a married person, then he should be stoned; a man who kills a soul not in retaliation for murder; and a man who apostatizes after becoming Muslim.' By Allah (SWT), I never committed adultery either during Ignorance days nor in Islam, and I have never killed a Muslim soul, and I have not apostatized since I became Muslim.”