Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) said: I heard the Prophet (peace and blessings be upon him) say: "After me there will be twelve caliphs: Abu Bakr al-Siddiq will not remain long; and the master of the mill of the Arabs will live praiseworthy and will be killed as a martyr." A man asked: Who is he, O Messenger of Allah? He (peace and blessings be upon him) said: "Umar bin al-Khattab." Then he (peace and blessings be upon him) turned to Uthman and said: "And as for you, the people will demand that you take off a shirt with which Allah has clothed you. By the One in whose hand is my soul, if you take it off, you will not enter Paradise until the camel passes through the eye of the needle."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 141