Sayyiduna Anas (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "By my order, close every door except the particular door of Abu Bakr. If I were to take anyone as a khalil (intimate friend), I would have taken Abu Bakr as a khalil."
Al-Bazzar recorded it, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14308