Musannaf Ibn Abi Shayba 27:413

Abu Mu’awiyah narrated to us, from al-A’mash, from Khaythama, from Masruq, from ‘Aisha, she said: When ‘Uthman was killed, you left him like a garment purified of filth, then you brought him near and slaughtered him as a ram is slaughtered. This [the killing] was only after that [the purification]. Masruq said to her: "Did you write to people commanding them to revolt?" ‘Aisha said: "No, by the One in whom the believers believe and in whom the disbelievers disbelieve, I did not write to them a single black mark on a white page until I sat in this seat of mine." Al-A’mash said: They used to believe that it was written on her behalf.