ENOfficial
Abu Huraira reported the Prophet (ﷺ) as saying, "Hell was kindled for a thousand years till it became red, then it was kindled for a thousand years till it became white, then it was kindled for a thousand years till it became black, and it is black and dark." Tirmidhi transmitted it.
Source: sunnah.com
Other translations
Arabic
عَنْ أَبِي هُرَيْرَةَ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «أُوقِدَ عَلَى النَّارِ أَلْفَ سَنَةٍ حَتَّى احْمَرَّتْ ثُمَّ أُوقِدَ عَلَيْهَا أَلْفَ سَنَةٍ حَتَّى ابْيَضَّتْ ثُمَّ أُوقِدَ عَلَيْهَا أَلْفَ سَنَةٍ حَتَّى اسْوَدَّتْ فَهِيَ سَوْدَاءُ مُظْلِمَةٌ» . رَوَاهُ التِّرْمِذِيّ
sunnah.com