The Prophet ﷺ said, "Boiling water will be poured over their heads. It will penetrate until it reaches the inside of the body, stripping out everything within until it passes out through the feet. This is the melting. Then he will be restored to what he was."
عن النبي ﷺ قال: إن الحميم ليصب على رؤوسهم، فينفذ الحميم حتى يخلص إلى جوفه، فيسلت ما في جوفه حتى يمرق من قدميه- وهو الصهر- ثم يعاد كما كان.
Tirmidhi (2582), Ahmad (8864), and Hakim (2/387) all narrated it through the route of Abdullah bin Mubarak, who reported to us from Saeed bin Yazid, from Abu Samh, from Ibn Hujayra, from Abu Hurairah, who related it.Tirmidhi said, "This is a hasan sahih gharib hadith, and Ibn Hujayra is Abdul-Rahman bin Hujayra Masri." Hakim said, "Its isnad is sahih."I say, its isnad is hasan because of what has been said about Abu Samh, who is Darraj bin Saman. His narrations are hasan except when he narrates from Abu Haytham, and this narration is not from Abu Haytham.