Al-Matalib al-'Aliyah 4390 — The killing of Uthman bin Affan

It is narrated from Imam al-Hasan al-Basri (may Allah have mercy on him) that he said: "I saw the people who were speaking improperly against Sayyiduna Uthman (may Allah be pleased with him) and grappling and quarrelling in the mosque to such an extent that (because of the dense crowd) I could not even see the expanse of the sky. Meanwhile a man from the blessed chambers of the Prophet (peace and blessings be upon him) called out, pointing to the Qur'an: 'Do you not know that Muhammad (peace and blessings be upon him) is completely free of and unconnected with whoever creates division in his religion and splits into sects?' Then he recited this verse: 'Indeed, those who have divided their religion and become sects, you have nothing to do with them' [Surah al-An'am: 159]."
Imam Ahmad bin Mani' recorded it in his Musnad, and this report is an authentic reflection of the conditions in the period of the trial (fitnah) of Uthman (may Allah be pleased with him).