The Prophet ﷺ said, "The thickness of the disbeliever's skin is forty-two cubits, his molar is like Mount Uhud, and his seat in Hell is the distance between Makkah and Madinah."
عن النبي ﷺ قال: إن غلظ جلد الكافر اثنان وأربعون ذراعا، وإن ضرسه مثل أحد، وإن مجلسه من جهنم كما بين مكة والمدينة.
Tirmidhi (2577) narrated it, and this is his wording, as did Ibn Abu Asim in Sunnah (610), Ibn Hibban (7486), Hakim (4/595), and Bayhaqi in Asma wal-Sifat (743), all of them by way of Ubaydullah bin Musa, who said, Shayban informed us, from Amash, from Abu Salih, from Abu Hurairah, who related it. Its chain of transmission is sahih. Tirmidhi said, "This is a hasan sahih hadith." Hakim said, "This is a sahih hadith according to the criteria of the two Shaykhs."