That a man came to him (while two groups of Muslims were fighting) and said, "O Abu ʿAbdur Rahman! Don't you hear what Allah has mentioned in His Book: 'And if two groups of believers fight against each other...' (49.9) So what prevents you from fighting as Allah has mentioned in His Book?"' Ibn ʿUmar said, "O son of my brother! I would rather be blamed for not fighting because of this Verse than to be blamed because of another Verse where Allah says: 'And whoever kills a believer intentionally..." (4.93) Then that man said, "Allah says:-- 'And fight them until there is no more afflictions (worshipping other besides Allah) and the religion (i.e. worship) will be all for Allah (Alone)" (8.39) Ibn ʿUmar said, "We did this during the lifetime of Messenger of Allah ﷺ when the number of Muslims was small, and a man was put to trial because of his religion, the pagans would either kill or chain him; but when the Muslims increased (and Islam spread), there was no persecution." When that man saw that Ibn ʿUmar did not agree to his proposal, he said, "What is your opinion regarding ʿAli and ʿUthman?" Ibn ʿUmar said, "What is my opinion regarding ʿAli and ʿUthman? As for ʿUthman, Allah forgave him and you disliked to forgive him, and ʿAli is the cousin and son-in-law of Messenger of Allah ﷺ ." Then he pointed out with his hand and said, "And that is his daughter's (house) which you can see." (Using translation from Bukhārī 4650)
ذَكَرَ اللهُ فِي كِتَابِهِ {وَإِنْ طَائِفَتَانِ مِنَ الْمُؤْمِنِينَ اقْتَتَلُوا} [الحجرات 9] فَمَا يَمْنَعُكَ أَنْ تُقَاتِلَ كَمَا ذَكَرَ اللهُ فِي كِتَابِهِ؟ فَقَالَ يَا ابْنَ أَخِي أَعْبُرُ بِهَذِهِ الْآيَةِ وَلَا أُقَاتِلُ أَحَبُّ إِلِيَّ مِنْ أَنْ أَعْبُرَ بِالْآيَةِ الَّتِي قَالَ اللهُ ﷻ قَبْلَهَا {وَمَنْ يَقْتُلْ مُؤْمِنًا مُتَعَمِّدًا فَجَزَاؤُهُ جَهَنَّمُ} [النساء 93] الْآيَةَ قَالَ فَإِنَّ اللهَ قَالَ {قَاتِلُوهُمْ حَتَّى لَا تَكُونَ فِتْنَةٌ} [البقرة 193] قَالَ ابْنُ عُمَرَ قَدْ فَعَلْنَاهُ عَلَى عَهْدِ رَسُولِ اللهِ ﷺ إِذْ كَانَ الْإِسْلَامُ قَلِيلًا وَكَانَ الرَّجُلُ يُفْتَنُ عَنْ دِينِهِ أَمَّا أَنْ يَقْتُلُوهُ أَوْ يُوْثِقُوهُ حَتَّى ظَهَرَ الْإِسْلَامُ وَلَمْ تَكُنْ فِتْنَةٌ؟ فَلَمَّا رَأَى أَنَّهُ لَا يُوَافِقُهُ فِيمَا يُرِيدُ قَالَ فَمَا قَوْلُكَ فِي عَلِيٍّ وَعُثْمَانَ ؓ ؟ فَقَالَ ابْنُ عُمَرَ أَمَّا عُثْمَانُ فَقَدْ عَفَا اللهُ عَنْهُ فَكَرِهْتُمْ أَنْ تَعْفُوا عَنْهُ وَأَمَّا عَلِيٌّ فَابْنُ عَمِّ رَسُولِ اللهِ ﷺ وَخَتَنُهُ وَأَشَارَ بِيَدِهِ فَقَالَ هَذَا بَيْتُهُ حَيْثُ تَرَوْنَ