The Prophet ﷺ said, "The thickness of the disbeliever's skin is forty-two cubits, his molar tooth is like Mount Uhud, and his seat in Hell is as vast as the distance between Mecca and Medina."This is a hasan sahih gharib hadith from the narration of Amash.
حدثنا عباس الدوري حدثنا عبيد الله بن موسى أخبرنا شيبان عن الأعمش عن أبي صالح
عن النبي ﷺ قال إن غلظ جلد الكافر اثنان وأربعون ذراعا وإن ضرسه مثل أحد وإن مجلسه من جهنم كما بين مكة والمدينة هذا حديث حسن صحيح غريب من حديث الأعمش
Its chain is daif. Ibn Abu Asim narrated it in his Sunnah, no. 610, from the hadith of Ubaydullah bin Musa with the same wording. Ibn Hibban graded it sahih, no. 2616, as did Hakim, who said it meets the criteria of the two Shaykhs, 4/595, and Dhahabi agreed with him. Amash conceals defects in his chains of transmission, and here he narrated it using the ambiguous formula "an" rather than affirming direct hearing. See no. 2579.The hadith has corroborating narrations in Ahmad, 2/328, 334, and elsewhere, without the phrase "Makkah and Madinah." This wording is rejected, and the following hadith makes it unnecessary.