What is Ibn Tamiyyah's evidence for the claim that Hell will be empty eventually?

The Qur'an clearly states that Hell is eternal. Of course I do not think Ibn Tamiyyah is correct, but I am asking because it is unusual for someone who so repeatedly talked of and condemned bid'ah, and creates such a huge one himself. >From his book > >ﻭﺣﻴﻨﺌﺬ ﻓﻴﺤﺘﺞ ﻋﻠﻰ ﻓﻨﺎﺋﻬﺎ ﺑﺎﻟﻜﺘﺎﺏ ﻭﺍﻟﺴﻨﺔ، ﻭﺃﻗﻮﺍﻝ ﺍﻟﺼﺤﺎﺑﺔ – ﻣﻊ ﺃﻥ ﺍﻟﻘﺎﺋﻠﻴﻦ ﺑﺒﻘﺎﺋﻬﺎ ﻟﻴﺲ ﻣﻌﻬﻢ ﻛﺘﺎﺏ، ﻭﻻ ﺳﻨﺔ ﻭﻻ ﺃﻗﻮﺍﻝ ﺍﻟﺼﺤﺎﺑﺔ -. ﺃﻫــــ > >“In which case, the argument for the ending of Hellfire is supported by the Quran, the Sunnah, and the statements of the Sahabah; while the affirmers of its eternality have with them no Quran, no Sunnah, and no statements of the Sahabah.” He even claims that he has the Qur'an on his side. I just want to know what is his side of the argument other than the fact that he thinks eternal hellfire is against "Divine wisdom"? (the "contradiction of divine wisdom" claim is also from his book)