Musnad Ahmad 28:201

Yahya narrated to us, from Ibn ‘Ajlan, from ‘Amr ibn Shu‘ayb, from his father, from his grandfather, that the Prophet, peace and blessings of Allah be upon him, said: "The arrogant will be gathered on the Day of Resurrection like tiny ants in the forms of people. Everything small will be above them, until they enter a prison in Hell called 'Bulas.' The fire of fires will rise above them, and they will be given to drink from 'tinat al-khabal' (the discharge of the people of Hell), which is the dregs of the people of Hell."