Uthman looked down at those besieging him and said, "Why are you trying 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, who must be stoned; one who kills another deliberately, who must be killed in retaliation; or one who apostatizes after embracing Islam, who must be put to death.' By Allah, I never committed adultery, neither in the days of ignorance nor in Islam, I never killed anyone such 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."
أن عثمان 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. فو الله ما زنيت في جاهلية ولا في إسلام، ولا قتلت أحدا فأقيد نفسي منه، ولا ارتددت منذ أسلمت إني أشهد أن لا إله إلا الله، وأن محمدا عبده ورسوله.
Ahmad (452) narrated it, and this is his wording, as did Nasai (4057), Bazzar in his Musnad (9/2), and Abu Asim in Diyat (111) in abridged form, all of them from the hadith of Ishaq bin Sulayman Razi, who said, I heard Mughira bin Muslim narrate it from Matar Warraq, from Nafi, from Ibn Umar, and he related it.Matar Warraq is disputed, but he is considered acceptable for corroboration, and Yaala bin Hakeem has corroborated him, narrating from Nafi. Bazzar narrated it in his Musnad from Muhammad bin Muamar, who said, Rawh bin Ubada narrated to us, who said, Saeed bin Abu Aruba narrated to us, from Yaala bin Hakeem, with his chain of transmission.