Musnad Ahmad 31:113

Hassan and ‘Affan narrated to us, they said: Hammad ibn Salamah narrated to us, from Sa’id al-Jurayri, from Abu Nadrah, from Abu Sa’id al-Khudri, who said: The Messenger of Allah (ﷺ) said: "The person among the people of the Fire with the lightest punishment is a man who has two sandals on his feet, from which his brain boils. Among them are those who are in the Fire up to their ankles, with the punishment flowing over them; and among them are those who are in the Fire up to their knees, with the punishment flowing over them; and among them are those who are submerged in the Fire up to their earlobes, with the punishment flowing over them; and among them are those who are in the Fire up to their chest, with the punishment flowing over them; and among them are those who are submerged in the Fire." ‘Affan said: "With the punishment flowing over them, he is submerged."