Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said, regarding the saying of Allah Almighty: "The Fire will scorch their faces, and they will be grim-faced therein" [Surah al-Mu'minun: 104]: "Have you not seen scorched heads, how their teeth become exposed and their lips shrink back?"
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9089