Sahih Muslim Book 1, Hadith Number 390.

Chapter : Pertaining to the words of the Apostle of Allah (may peace be upon him): “I would be the first among people to Intercede in the Paradise and among the Apostles I would have the largest following”.

Abu Huraira said: The Messenger of Allah (may peace be upon him) said: Every Messenger is endowed with a prayer which is granted and by which he would (pray to his Lord) and it would he granted for him. I have, however, reserved my prayer for the intercession of my Ummab on the Day of Resurrection.