Musannaf Ibn Abi Shayba 36:545

Isma’il ibn ‘Ulayyah narrated to us, from Ibn ‘Awn, from al-Hasan, who said: Wathab informed me—and he was among those who attained the manumission of the Commander of the Faithful, ‘Umar, and he used to be in the presence of ‘Uthman—he said: I saw on his (Uthman’s) hip the mark of two stab wounds, as if they were two cauterizations; he was stabbed with them on the Day of the House, the house of ‘Uthman. He said: The Commander of the Faithful, ‘Uthman, sent me, saying: "Call al-Ashtar for me." So he came. He said—Ibn ‘Awn said: I think he said: "So I threw a cushion for the Commander of the Faithful, and a cushion for him." He (Uthman) said: "O Ashtar, what do the people want from me?" He said: "Three things, there is no escape from one of them. They give you the choice between abdicating their affair for them and saying: 'This is your affair, choose whom you wish,' or that you allow retaliation against yourself, or if you refuse these two, then the people will kill you." He said: "Is there no escape from one of them?" He said: "There is no escape from one of them." He said: "As for abdicating their affair for them, I will never take off a garment that Allah, the Mighty and Majestic, has clothed me with." Ibn ‘Awn said: And someone other than al-Hasan said: "That I be brought forward and my neck be struck is more beloved to me than that I should strip the affair of the nation of Muhammad from one another." Ibn ‘Awn said, in his own words: "And nor will I allow retaliation against myself, for by Allah, I know that my two companions (the Prophet and Abu Bakr) before me used to allow retaliation against themselves, but my body cannot endure retaliation. And as for them killing me, by Allah, if they kill me, they will never love one another after me, and they will never fight an enemy together after me." He said: So al-Ashtar stood up and left. We waited and said: "Perhaps the people (will desist)." Then a small man came, as if he were a wolf, and he peered through the door, then returned. Then Muhammad ibn Abi Bakr stood up with thirteen (men) until he reached ‘Uthman. He grabbed his beard and pulled it until I heard the sound of his teeth (grinding). He said: "What did Mu’awiyah avail you? What did Ibn ‘Amir avail you? What did your letters avail you?" He (Uthman) said: "Release my beard, son of my brother; release my beard, son of my brother." He said: And I saw him seek help from a man among the people to assist him, so he stood up to him with an arrowhead and stabbed him in his head, and it fixed him (to the ground). He said: Then what? He said: Then they entered upon him until they killed him.