Musnad Ahmad 31:746

'Affan narrated to us, Hammad narrated to us, from Sa'id al-Jurayri, from Abu Nadra, from Abu Sa'id al-Khudri, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, the person among the people of the Fire with the lightest punishment is a man wearing two sandals of fire, from which his brain boils, along with the continuation of the punishment. And among them is he who is in the Fire up to his ankles, along with the continuation of the punishment. And among them is he who is in the Fire up to his knees, along with the continuation of the punishment. And among them is he who is in the Fire up to his earlobes, along with the continuation of the punishment. And among them is he who is in the Fire up to his chest, along with the continuation of the punishment, having been submerged."