It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "If I were to take anyone as a khalil (intimate friend), I would take Abu Bakr; but he is my brother and my companion, and Allah has taken your companion as His khalil."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10070