Sahih Muslim Book 41, Hadith Number 6926.
Chapter : The last hour would come when the Romans would have the maximum population.
Mustaurid 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. This reached ‘Amr b. al-‘As and he said: What are these ahadith which are being transmitted from you and which you claim to have heard from Allah’s Messenger (may peace be upon him)? Mustaurid said to him: I stated only that which I heard from Allah’s Messenger (may peace be upon him). Thereupon ‘Amr said: If you state this (it is true), for they have the power of tolerance amongst people at the time of turmoil and restore themselves to sanity after trouble, and are good amongst people so far as the destitute and the weak are concerned.