Sahih Muslim Book 1, Hadith Number 386.

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 reported: The Messenger of Allah (may peace be upon him) said: There is for every apostle a prayer, and I intend (if Allah so willed) that I would reserve my prayer for the intercession of my Ummah on the Day of Resurrection.