I went to Abu Wail to ask him (about those who had rebelled against ʿAli). On that Abu Wail said, "We were at Siffin (a city on the bank of the Euphrates, the place where me battle took place between ʿAli and Muawiya) A man said, "Will you be on the side of those who are called to consult Allah's Book (to settle the dispute)?" ʿAli said, 'Yes (I agree that we should settle the matter in the light of the Qur'an)." ' Some people objected to ʿAli's agreement and wanted to fight. On that Sahl bin Hunaif said, 'Blame yourselves! I remember how, on the day of Al-Hudaibiya (i.e. the peace treaty between the Prophet ﷺ and the Quraish pagans), if we had been allowed to choose fighting, we would have fought (the pagans). At that time ʿUmar came (to the Prophet) and said, "Aren't we on the right (path) and they (pagans) in the wrong? Won't our killed persons go to Paradise, and theirs in the Fire?" The Prophet replied, "Yes." ʿUmar further said, "Then why should we let our religion be degraded and return before Allah has settled the matter between us?" The Prophet ﷺ said, "O the son of Al-Khattab! No doubt, I am Messenger of Allah ﷺ and Allah will never neglect me." So ʿUmar left the place angrily and he was so impatient that he went to Abu Bakr and said, "O Abu Bakr! Aren't we on the right (path) and they (pagans) on the wrong?" Abu Bakr said, "O the son of Al-Khattab! He is Messenger of Allah ﷺ, and Allah will never neglect him." Then Sura Al-Fath (The Victory) was revealed."
رَجُلٌ أَلَمْ تَرَ إِلَى الَّذِينَ يُدْعَوْنَ إِلَى كِتَابِ اللَّهِ فَقَالَ عَلِيٌّ نَعَمْ فَقَالَ سَهْلُ بْنُ حُنَيْفٍ اتَّهِمُوا أَنْفُسَكُمْ فَلَقَدْ رَأَيْتُنَا يَوْمَ الْحُدَيْبِيَةِ يَعْنِي الصُّلْحَ الَّذِي كَانَ بَيْنَ النَّبِيِّ ﷺ وَالْمُشْرِكِينَ وَلَوْ نَرَى قِتَالاً لَقَاتَلْنَا فَجَاءَ عُمَرُ فَقَالَ أَلَسْنَا عَلَى الْحَقِّ وَهُمْ عَلَى الْبَاطِلِ أَلَيْسَ قَتْلاَنَا فِي الْجَنَّةِ وَقَتْلاَهُمْ فِي النَّارِ قَالَ بَلَى قَالَ فَفِيمَ أُعْطِي الدَّنِيَّةَ فِي دِينِنَا وَنَرْجِعُ وَلَمَّا يَحْكُمِ اللَّهُ بَيْنَنَا فَقَالَ يَا ابْنَ الْخَطَّابِ إِنِّي رَسُولُ اللَّهِ وَلَنْ يُضَيِّعَنِي اللَّهُ أَبَدًا فَرَجَعَ مُتَغَيِّظًا فَلَمْ يَصْبِرْ حَتَّى جَاءَ أَبَا بَكْرٍ فَقَالَ يَا أَبَا بَكْرٍ أَلَسْنَا عَلَى الْحَقِّ وَهُمْ عَلَى الْبَاطِلِ قَالَ يَا ابْنَ الْخَطَّابِ إِنَّهُ رَسُولُ اللَّهِ ﷺ وَلَنْ يُضَيِّعَهُ اللَّهُ أَبَدًا فَنَزَلَتْ سُورَةُ الْفَتْحِ