Jahannam (Hebrew, gehinnom; Greek, gehenna) is the Islamic hell mentioned frequently in the Qur’an, It has seven gates (Qur’an 59. 71; 15. 43) and different levels, the lowest being the tree Zaqqum and a cauldron of pitch and fire. Punishments are in accord to the gravity of sins–a theme much elaborated on by later commentators. The Qur’an is not clear if the punishments exacted on Muslin sinners last forever, and Muhammad’s statement, “The condemned will be cast into fire, to dwell there so long as the heavens and earth shall last, unless God wills otherwise,” does not make it clear as whether Allah ever would “will otherwise.” It is theorized, by some, that such statements, which are not definitive, merely serve to protect omnipotent freedom. Neither is it clear whether the new heavens and the new earths will be created when the present ones are ended, in a way corresponding to Allah’s renewal of the skins of the damned, so that the fire can burn them again. In contrast, a kafir is generally thought to be punished eternally. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, “Hell,” pp. 420-421