Surah 104. Al-Humazah, Ayah 7

I.e., originating in their hearts - thus clearly alluding to the spiritual nature of the "fire" in the sinners' belated realization of their guilt.

The Fire of Punishment mounts right up to the hearts and minds of such men, and shuts them out of the love of their fellows. "Heart" in Arabic means not only the seat of affection, pity, charity, etc., but also of understanding and intelligent appreciation of things.