It is narrated from Hamzah bin Abdullah bin Umar (may Allah be pleased with them both) that he was sitting with his father, Sayyiduna Abdullah bin Umar (may Allah be pleased with them both), when a man from Iraq came and said: "O Abu Abd al-Rahman, by Allah, I have striven eagerly to adopt your way, to follow you in the matter of the divisions among people, and to keep away from evil as much as I can. But I read a decisive verse in the Book of Allah which has gripped my heart (with worry), so tell me about it: what is your view of this saying of Allah, the Mighty and Majestic: 'And if two groups of the believers fight each other, then make peace between them. But if one of them transgresses against the other, then fight the one that transgresses until it returns to the command of Allah. Then if it returns, make peace between them with justice, and act justly; indeed, Allah loves those who act justly' [Surah al-Hujurat: 9] ?" At this Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: "What have you to do with this matter? Go away from me." So the man got up and left, until when he had gone out of our sight, Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) turned to us and said: "I have not felt in myself such unease (and regret) over anything as I have felt over the matter of this verse: that I did not fight this transgressing group as Allah commanded me." This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.