Bukhari

Narrated 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." Narrated Nafi` (through another group of sub-narrators): A man came to Ibn `Umar and said, "O Abu `Abdur Rahman! What made you perform Hajj in one year and Umra in another year and leave the Jihad for Allah' Cause though you know how much Allah recommends it?" Ibn `Umar replied, "O son of my brother! Islam is founded on five principles, i.e. believe in Allah and His Apostle, the five compulsory prayers, the fasting of the month of Ramadan, the payment of Zakat, and the Hajj to the House (of Allah)." The man said, "O Abu `Abdur Rahman! Won't you listen to why Allah has mentioned in His Book: 'If two groups of believers fight each other, then make peace between them, but if one of then transgresses beyond bounds against the other, then you all fight against the one that transgresses. (49.9) and:--"And fight them till there is no more affliction (i.e. no more worshiping of others along with Allah)." Ibn `Umar said, "We did it, during the lifetime of Allah's Messenger when Islam had only a few followers. A man would be put to trial because of his religion; he would either be killed or tortured. But when the Muslims increased, there was no more afflictions or oppressions." The man said, "What is your opinion about `Uthman and `Ali?" Ibn `Umar said, "As for `Uthman, it seems that Allah has forgiven him, but you people dislike that he should be forgiven. And as for `Ali, he is the cousin of Allah's Messenger and his son-in-law." Then he pointed with his hand and said, "That is his house which you see."

‘And Uthman bin Salih narrated in more detail that Abdullah bin Wahb narrated to him, he was informed by so-and-so, Abdullah bin Rabee’ah and Haywah bin Shurayh, they were informed by Bakr bin Amr Mu’afiri, from Bukayr bin Abdullah, from Nafi’, that:
A man (Hakeem) came to Ibn Umar (may Allah be pleased with them both) and said, “O Abu Abdur-Rahman! What is the matter with you that you perform Hajj one year and ‘Umrah the next year, but do not participate in Jihad in the way of Allah, even though you know how much Allah has encouraged Jihad?”
Ibn Umar (may Allah be pleased with them both) replied, “My nephew! Islam is built upon five things: to have faith in Allah and His Messenger, to perform the five daily prayers, to fast in Ramadan, to give Zakat, and to perform Hajj.”
He said, “O Abu Abdur-Rahman! Do you not know what Allah the Exalted has said in the Book of Allah «وإن طائفتان من المؤمنين اقتتلوا فأصلحوا بينهما‏»: ‘And if two groups of the believers fight each other, make peace between them.’ Up to Allah’s statement «إلى أمر الله‏» (and Allah the Exalted’s statement: ‘And fight them’) until there is no more discord.”
Ibn Umar (may Allah be pleased with them both) said, “We fulfilled this obligation during the time of the Messenger of Allah (peace and blessings be upon him). At that time, the Muslims were very few and the disbelievers were many, so the disbelievers would corrupt the religion of the Muslims, sometimes killing the Muslims, sometimes causing them harm, until the Muslims became many and the discord disappeared.”

Then that person asked, "Well, tell me, what is your belief regarding Uthman and Ali (may Allah be pleased with them both)?" He replied, "Allah has forgiven Uthman (may Allah be pleased with him) for his fault, but you do not consider this forgiveness to be good. As for Ali (may Allah be pleased with him), he was the cousin of the Noble Prophet (peace and blessings of Allah be upon him) and his son-in-law." And with a gesture of his hand, he indicated, "Look, his house was adjacent to the house of the Noble Prophet (peace and blessings of Allah be upon him)."