Musnad Ahmad 25:831

Hassan and 'Affan—the meaning being the same—said: Hammad ibn Salamah narrated to us, from Thabit al-Bunani, from Abu 'Uthman al-Nahdi, from Ibn 'Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The person among the people of the Fire with the lightest punishment is Abu Talib; upon his feet are two sandals of fire, from which his brain boils."