Musannaf Ibn Abi Shayba 27:416

Husayn ibn Ali narrated to us, from Mujammi, who said: Abd al-Rahman ibn Abi Layla entered upon al-Hajjaj. Al-Hajjaj said to those sitting with him, "If you wish to look at a man who insults the Commander of the Faithful, Uthman, then here he is before you," meaning Abd al-Rahman. Abd al-Rahman said, "I seek refuge in Allah, O Prince, that I should insult Uthman. Indeed, a verse in the Book of Allah restrains me from that. Allah says: 'For the poor emigrants who were expelled from their homes and their properties, seeking bounty from Allah and [His] approval and supporting Allah and His Messenger, [there is also a share]. Those are the truthful.'" He said: "And Uthman was one of them."