Abu Wa'il narrates: I said to Sayyiduna Abd al-Rahman bin Awf (may Allah be pleased with him): "How is it that you pledged allegiance to Sayyiduna Uthman (may Allah be pleased with him) and left Sayyiduna Ali (may Allah be pleased with him)?" He said: "What is my fault? I began with Ali and said: 'I will pledge allegiance to you on the condition that you will act according to the Book of Allah, the Sunnah of His Messenger, and the way of Sayyiduna Abu Bakr (may Allah be pleased with him) and Sayyiduna Umar (may Allah be pleased with him).' He said: 'As far as I am able (I will act on it).'" Sayyiduna Abd al-Rahman (may Allah be pleased with him) says: "Then I offered the same to Sayyiduna Uthman (may Allah be pleased with him), and he accepted it (that is, he said: I will do just that)."
Abdullah bin Ahmad recorded it; its chain contains Sufyan bin Waki', who is extremely da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الخلافة / 8945