رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 398
The Book of Miscellany
Fear (of Allah)
وَعَنِ النُّعْمَانِ بْنِ بَشِيرٍ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ : سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ يَقُولُ: إِنَّ أَهْوَنَ أَهْلِ النَّارِ عَذَابًا يَوْمَ الْقِيَامَةِ لَرَجُلٌ يوضع فِي أَخْمَصِ قَدَمَيْهِ جَمْرَتَانِ يَغْلِي مِنْهُمَا دِمَاغُهُ، ما يرى أن أحد أَشَدُّ مِنْهُ عَذَابًا، وَإِنَّهُ لأَهْوَنُهُمْ عَذَابًا" (( مُتَّفَقٌ عَلَيْهِ))
Nu'man bin Bashir (May Allah be pleased with them) reported: Messenger of Allah (ﷺ) said, "The least tortured man on the Day of Resurrection is one underneath whose feet will be placed two live coal, and his brain will be boiling, and he would think that he is the most tortured, while he is the least tortured". [Al-Bukhari and Muslim].
Riyad as-Salihin, 398