Sahih Muslim Book 41, Hadith Number 7050.

Chapter : Approach of the Last Hour.

‘Aisha reported that when the desert Arabs came to Allah’s Messenger (may peace be upon him) they asked about the Last Hour as to when that would come. And he looked towards the youngest amongst them and said: If he lives he would not grow very old that he would find your Last Hour coming to you the would see you dying).