Musnad Abu Ya'la al-Mawsili 131:18

'Uthman and Abu Bakr, the sons of Abi Shaybah, narrated to us, they said: Mu'awiyah ibn Hisham narrated to us, from Sufyan al-Thawri, from al-Mukhtar ibn Fulful, from Anas ibn Malik, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "I am the first one to knock on the door of Paradise."