Musnad Abu Ya'la al-Mawsili 131:22

Abu Bakr ibn Abi Shaybah narrated to us, Husayn ibn Ali narrated to us, from Za'idah, from al-Mukhtar ibn Fulful, who said: Anas said: The Prophet, may Allah bless him and grant him peace, said: "I am the first intercessor in Paradise."