Sijjin

Sijjin (Arabic: سِجِّين lit. Netherworld, Underworld, Chthonian World) is in Islamic belief either a prison, vehement torment or straitened circumstances at the bottom of Jahannam or hell, below the earth (compare Greek Tartarus),^: 166 or, according to a different interpretation, a register for the damned or record of the wicked, which is mentioned in Quran 83:7. Sijjin is also considered to be a place for the souls of unbelievers until resurrection.^: 21

The idea that there is a hell underneath earth's surface roots in the Quran, which speaks about "seven earths" (65:12), while describing hell as a subterranean pit, divided into seven compartments.^: 166 Thus, many Muslim authors coincided hell with layers of the earth with sijjin at the bottom.^: 166 For the lowest layer of hell, the term al-asfal is used too.^: 42 The antithesis of Sijjin is Illiyin.