Musannaf Ibn Abi Shayba 27:414

Shababa narrated to us, he said: Shu'bah narrated to us, from Ja'far ibn Iyas, from Yusuf ibn Mahak, from Muhammad ibn Hatib, he said: I heard Ali delivering a sermon, saying: "Indeed, those for whom the best [reward] has preceded from Us, they are from it [the Fire] kept far away." He said: Uthman is among them.