Nafi' said: "When Sayyiduna Uthman (may Allah be pleased with him) was martyred, Sayyiduna Ali (may Allah be pleased with him) came to Sayyiduna Ibn Umar (may Allah be pleased with them both) and said: You are beloved among the people, so set out for Syria. Ibn Umar (may Allah be pleased with them both) said: By my kinship with you, my companionship with the Prophet (peace and blessings be upon him), and the ties of relationship between us! (I will not do it.) So he did not press him again."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12991