أَخْبَرَنِي إِبْرَاهِيمُ بْنُ يَعْقُوبَ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ عِيسَى، قَالَ حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، قَالَ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، قَالَ حَدَّثَنِي أَبُو أُمَامَةَ بْنُ سَهْلٍ، وَعَبْدُ اللَّهِ بْنُ عَامِرِ بْنِ رَبِيعَةَ، قَالاَ كُنَّا مَعَ عُثْمَانَ وَهُوَ مَحْصُورٌ - وَكُنَّا إِذَا دَخَلْنَا مَدْخَلاً نَسْمَعُ كَلاَمَ مَنْ بِالْبَلاَطِ - فَدَخَلَ عُثْمَانُ يَوْمًا ثُمَّ خَرَجَ فَقَالَ إِنَّهُمْ لَيَتَوَاعَدُونِي بِالْقَتْلِ . قُلْنَا يَكْفِيكَهُمُ اللَّهُ . قَالَ فَلِمَ يَقْتُلُونِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " لاَ يَحِلُّ دَمُ امْرِئٍ مُسْلِمٍ إِلاَّ بِإِحْدَى ثَلاَثٍ رَجُلٌ كَفَرَ بَعْدَ إِسْلاَمِهِ أَوْ زَنَى بَعْدَ إِحْصَانِهِ أَوْ قَتَلَ نَفْسًا بِغَيْرِ نَفْسٍ " . فَوَاللَّهِ مَا زَنَيْتُ فِي جَاهِلِيَّةٍ وَلاَ إِسْلاَمٍ وَلاَ تَمَنَّيْتُ أَنَّ لِي بِدِينِي بَدَلاً مُنْذُ هَدَانِي اللَّهُ وَلاَ قَتَلْتُ نَفْسًا فَلِمَ يَقْتُلُونَنِي
Abu Umamah bin Sahl and 'Abdullah bin 'Amir bin Rabi'ah said: "We were with 'Uthman when he was under siege and we could hear what was said from Al-Balat. 'Uthman came in one day, then he came out, and said: 'They are threatening to kill me.' We said: 'Allah will suffice you against them.' He said: 'Why would they kill me? I heard the Messenger of Allah [SAW] say: It is not permissible to shed the blood of a Muslim except in one of three cases: A man who reverts to Kufr after becoming Muslim, or commits adultery after being married, or one who kills a soul unlawfully. By Allah, I did not commit adultery during Jahiliyyah or in Islam, I never wished to follow any other religion since Allah guided me, and I have never killed anyone, so why do they want to kill me?'" Translation Not Available
Book Ref: Sunan An Nisai Book 37 Hadith 4019
Web Ref: Sunan An Nisai Vol 5 Book 37 Hadith 4024