Hell had been lit for one thousand years until its flames became red. Again it was heated for another thousand years till its colour became white. Still again it was burnt for further thousand years and its white color flames turned pitch black.
Answer:
The Hadith is narrated by Imaam Tirmidhi (RA) in his Jaami (vol.2 pg.86; HM Saeed)
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai