Musnad Ahmad 26:205

Mu'awiyah ibn Hisham narrated to us, Sufyan narrated to us, from 'Abd al-Malik ibn 'Umayr, from Khalid ibn Rab'i, from 'Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, your companion is the intimate friend (Khalil) of Allah."