Abu Umama bin Sahl reported,

We were with Uthman while he was besieged in his house. There was a passageway in the house through which anyone who entered could hear what was being said by those on the paved area outside. Uthman went into it, and when he came back out to us, his color had changed.He said, "They are threatening to kill me right now."We said, "Allah will suffice you against them, Commander of the Faithful."He replied, "Why would they kill me? I heard the Messenger of Allah ﷺ say, 'The blood of a Muslim is not lawful except in one of three cases, disbelief after Islam, adultery after marriage, or killing a soul other than in retaliation for a soul.' By Allah, I never committed adultery, neither in the days of ignorance nor in Islam, nor have I ever wished to exchange my religion for another since Allah guided me, nor have I killed anyone. So for what would they kill me?"

عن أبي أمامة بن سهل قال

كنا مع عثمان وهو محصور في الدار، وكان في الدار مدخل من دخله سمع كلام من على البلاط، فدخله عثمان، فخرج إلينا وهو متغير لونه، فقال: إنهم ليتواعدوني بالقتل آنفا، قلنا: يكفيكهم الله يا أمير المؤمنين. قال: ولم يقتلوني؟ سمعت رسول الله ﷺ يقول: لا يحل دم امرئ مسلم إلا بإحدى ثلاث: كفر بعد إسلام، أو زنا بعد إحصان، أو قتل نفس بغير نفس فوالله ما زنيت في جاهلية ولا إسلام قط، ولا أحببت أن لي بديني بدلا منذ هداني الله، ولا قتلت نفسا. فبم يقتلوني؟