The Book Pertaining to the Turmoil and Portents of the Last Hour (Kitab Al-Fitan wa Ashrat As-Sa`ah)
Muslim :: Book 41 : Hadith 6925
Mustaurid al-Qurashi reported: I heard Allah's Messenger (may peace be upon him) as saying: The Last Hour would come (when) the Romans would form a majority amongst people. 'Amr said to him (Mustaurid Qurashi): See what you are saying? He said: I say what I heard from Allah's Messenger (may peace be upon him). Thereupon he said: If you say that, it is a fact for they have four qualities. They have the patience to undergo a trial and immediately restore themselves to sanity after trouble and attack again after flight. They (have the quality) of being good to the destitute and the orphans, to the weak and, fifthly, the good quality in them is that they put resistance against the oppression of kings.