Sahih Muslim Book 1, Hadith Number 384.

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 will come to the gate of Paradise on the Day of Resurrection and would seek its opening and the keeper would say: Who art thou? I would say: Muhammad. He would then say: It is for thee that I have been ordered, and not to open it for anyone before thee.