Sahih al-Bukhari 6561
صحيح البخاري#6561Sahihحَدَّثَنِي مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا غُنْدَرٌ، حَدَّثَنَا شُعْبَةُ، قَالَ سَمِعْتُ أَبَا إِسْحَاقَ، قَالَ سَمِعْتُ النُّعْمَانَ، سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ "إِنَّ أَهْوَنَ أَهْلِ النَّارِ عَذَابًا يَوْمَ الْقِيَامَةِ لَرَجُلٌ تُوضَعُ فِي أَخْمَصِ قَدَمَيْهِ جَمْرَةٌ يَغْلِي مِنْهَا دِمَاغُهُ".
Narrated An-Nu`man:I heard the Prophet (ﷺ) saying, "The person who will have the least punishment from amongst the Hell Fire people on the Day of Resurrection, will be a man under whose arch of the feet a smoldering ember will be placed so that his brain will boil because of it
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 81:150