Sahih Muslim 213 b
Nu'man b. Bashir reported:
The Messenger of Allah (ﷺ) said: Verily the least suffering for the inhabitants of Fire would be for him who would have two shoes and two laces of Fire (on his feet), and with these would boil his brain as boils the cooking vessel, and he would think that he would not see anyone in a more grievous torment than him, whereas he would be in the least torment.
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنِ الأَعْمَشِ، عَنْ أَبِي إِسْحَاقَ، عَنِ النُّعْمَانِ بْنِ بَشِيرٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ إِنَّ أَهْوَنَ أَهْلِ النَّارِ عَذَابًا مَنْ لَهُ نَعْلاَنِ وَشِرَاكَانِ مِنْ نَارٍ يَغْلِي مِنْهُمَا دِمَاغُهُ كَمَا يَغْلِي الْمِرْجَلُ مَا يَرَى أَنَّ أَحَدًا أَشَدُّ مِنْهُ عَذَابًا وَإِنَّهُ لأَهْوَنُهُمْ عَذَابًا ‏"‏ ‏.‏