Sahih Muslim Book 1, Hadith Number 414.

Chapter : Intercession of the Messenger of Allah (may peace be upon him) for Abu Talib and some remission for him on this account.

Nu’man b. Bashir was delivering an address and saying: I heard the Messenger of Allah (may peace be upon him) say: the least suffering for the inhabitants of Hell on the Day of Resurrection would be for the man under whose soles would be placed two embers and his brain would boil on account of them.