Musannaf Ibn Abi Shayba 27:782

Husayn ibn Ali narrated to us, from Umar ibn Dharr, who said: I was standing with al-Sha'bi one day, and a man came to him and said, "What do you say about Ali and Uthman?" He replied, "I am too wealthy [in good deeds] to have Ali and Uthman seek me out on the Day of Resurrection for an injustice."