Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "After me there will be twelve caliphs: Abu Bakr al-Siddiq will remain after me only a short while; and the man of the turning millstone will live praiseworthy and will die a martyr." It was asked: O Messenger of Allah, who is he? He (peace and blessings be upon him) said: "Umar bin al-Khattab." Then he (peace and blessings be upon him) turned to Sayyiduna Uthman (may Allah be pleased with him) and said: "And as for you, people will demand that you take off the garment that Allah, the Mighty and Majestic, has clothed you with. 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 / 12