Narrated Habib bin Abi Thabit:
I went to Abu Wail to ask him (about those who had rebelled against 'Ali). 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 'Ali 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)?" 'Ali said, 'Yes (I agree that we should settle the matter in the light of the Qur'an)." ' Some people objected to 'Ali'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 and the Quraish pagans), if we had been allowed to choose fighting, we would have fought (the pagans). At that time 'Umar 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." Umar 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 Allah's Apostle and Allah will never neglect me." So Umar 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 Allah's Apostle, and Allah will never neglect him." Then Sura Al-Fath (The Victory) was revealed."
• Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 367
• Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 367