Sahih Bukhari Volume 6, Book 65, Hadith 4515

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا عَبْدُ الْوَهَّابِ، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ أَتَاهُ رَجُلاَنِ فِي فِتْنَةِ ابْنِ الزُّبَيْرِ فَقَالاَ إِنَّ النَّاسَ قَدْ ضُيِّعُوا، وَأَنْتَ ابْنُ عُمَرَ وَصَاحِبُ النَّبِيِّ صلى الله عليه وسلم فَمَا يَمْنَعُكَ أَنْ تَخْرُجَ فَقَالَ يَمْنَعُنِي أَنَّ اللَّهَ حَرَّمَ دَمَ أَخِي‏.‏ فَقَالاَ أَلَمْ يَقُلِ اللَّهُ ‏{‏وَقَاتِلُوهُمْ حَتَّى لاَ تَكُونَ فِتْنَةٌ ‏}‏ فَقَالَ قَاتَلْنَا حَتَّى لَمْ تَكُنْ فِتْنَةٌ، وَكَانَ الدِّينُ لِلَّهِ، وَأَنْتُمْ تُرِيدُونَ أَنْ تُقَاتِلُوا حَتَّى تَكُونَ فِتْنَةٌ، وَيَكُونَ الدِّينُ لِغَيْرِ اللَّهِ‏

Narrated By Nafi' : During the affliction of Ibn Az-Zubair, two men came to Ibn 'Umar and said, "The people are lost, and you are the son of 'Umar, and the companion of the Prophet, so what forbids you from coming out?" He said, "What forbids me is that Allah has prohibited the shedding of my brother's blood." They both said, "Didn't Allah say, 'And fight then until there is no more affliction?" He said "We fought until there was no more affliction and the worship is for Allah (Alone while you want to fight until there is affliction and until the worship become for other than Allah."