Musnad Abu Ya'la al-Mawsili 109:164

Abu Hisham narrated to us, Ibn Fudayl narrated to us, al-Ajlah narrated to us, from Abu al-Zubayr, from Jabir, who said: When the day of al-Ta'if came, the Messenger of Allah (may Allah bless him and grant him peace) held a private conversation with Ali, and he prolonged his private conversation. Some of his companions said, "He has certainly prolonged the private conversation with his cousin." This reached him, so he said, "It is not I who held a private conversation with him, rather it is Allah who held a private conversation with him."