Sahih Muslim Book 1, Hadith Number 381.

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”.

Anas b. Malik reported: The Messenger of Allah (may peace be upon him) said: I would be the first among people to intercede in the Paradise and amongst the apostles I would have the largest following (on the Day of Resurrection).