The Messenger of Allah ﷺ said, "The molar of the disbeliever, or the canine tooth of the disbeliever, will be like Mount Uhud, and the thickness of his skin will be a journey of three days."
قال رسول الله ﷺ: ضرس الكافر أو ناب- الكافر- مثل أحد، وغلظ جلده مسيرة ثلاث.
Muslim narrated it in the Book of Paradise and the Description of Its Bliss (2851), from Surayj bin Yunus, who said, Humayd bin Abdul-Rahman told us, from Hasan bin Salih, from Harun bin Saad, from Abu Hazim, from Abu Hurairah, and he related it.As for His saying, "and We will admit them into deep, cool shade" [Nisa 4:57], it means dense, deep shade.