Musnad Abu Ya'la al-Mawsili 155:338

Al-Harith narrated to us, Marwan narrated to us, from Yazid ibn Kaysan, from Abu Hazim, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said to Abu Talib when death approached him: "Say: 'There is no god but Allah,' so that I may intercede for you on the Day of Resurrection." He said: "O son of my brother, were it not that Quraysh would reproach me, I would have gladdened your eye with it." Then it was revealed: "Indeed, you do not guide whom you love."