The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fada'il Al-Sahabah)
Muslim :: Book 31 : Hadith 5964
Abdullah b. Ja'far reported that one day Allah's Messenger (may peace be upon him) mounted me behind him and narrated to me something in secret which I would narrate to none amongst people.