It was narrated that 'Abdullah said:
"The Messenger of Allah said: 'I have no need of the friendship of any Khalil (close friend) but if I were to have taken anyone as a close friend, I would have taken Abu Bakr as a close friend, but your companion is the close friend of Allah,'" (One of the narrators) Waki' said: (by the phrase 'your companion'), he was referring to himself.
English reference: Vol. 1, Book 1, Hadith 93
Arabic reference: Book 1, Hadith 98