Musannaf Ibn Abi Shayba 34:113

Ubayd Allah narrated to us, from Isra'il, from Abu Ishaq, that a man narrated to him, saying: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, the first banner that will knock at the door of Paradise is my banner. And indeed, the first person to be granted permission for intercession is I, and there is no boast."