Abdullah bin Umar reported,

Uthman looked down upon those who were besieging him and said, "On what grounds are you going to kill me? I heard the Messenger of Allah ﷺ say, 'The blood of a Muslim is not lawful except in one of three cases. A man who commits adultery after marriage, in which case he is to be stoned. One who kills deliberately, in which case he is to be killed in retaliation. Or one who apostatizes after embracing Islam, in which case he is to be put to death.' By Allah, I never committed adultery, neither in the days of ignorance nor in Islam. I never killed anyone, that I should be killed in retaliation. And I have not apostatized since I embraced Islam. I bear witness that there is no god but Allah and that Muhammad is His servant and messenger."

حدثنا إسحاق بن سليمان قال سمعت مغيرة بن مسلم أبا سلمة يذكر عن مطر عن نافع

عن ابن عمر

أن عثمان رضي الله عنه أشرف على أصحابه وهو محصور فقال علام تقتلوني فإني سمعت رسول الله ﷺ يقول لا يحل دم امرئ مسلم إلا بإحدى ثلاث رجل زنى بعد إحصانه فعليه الرجم أو قتل عمدا فعليه القود أو ارتد بعد إسلامه فعليه القتل فوالله ما زنيت في جاهلية ولا إسلام ولا قتلت أحدا فأقيد نفسي منه ولا ارتددت منذ أسلمت إني أشهد أن لا إله إلا الله وأن محمدا عبده ورسوله