Allah said,

[وَقُودُهَا النَّاسُ وَالْحِجَارَةُ]

(whose fuel is men and stones,) indicating that the Children of Adam will be fuel for the Fire that will feed it,

[وَالْحِجَارَةُ]

(and stones) in reference to the idols that were worshipped, just as Allah said in another Ayah,

[إِنَّكُمْ وَمَا تَعْبُدُونَ مِن دُونِ اللَّهِ حَصَبُ جَهَنَّمَ]

(Certainly you and that which you are worshipping now besides Allah, are (but) fuel for Hell!) (21:98) `Abdullah bin Mas`ud, Mujahid, Abu Ja`far Al-Baqir and As-Suddi said that these are sulfur stones that are more putrid than rotten corpses, according to Mujahid. Allah's statement,

[عَلَيْهَا مَلَـئِكَةٌ غِلاَظٌ شِدَادٌ]

(over which are (appointed) angels stern (and) severe,) means, their nature of behavior is stern, because the mercy has been taken out of their hearts for those who disbelieve in Allah,

[شِدَادٌ]

(severe) meaning, their structure is powerful, strong and frightening,

[لاَّ يَعْصُونَ اللَّهَ مَآ أَمَرَهُمْ وَيَفْعَلُونَ مَا يُؤْمَرُونَ]

(who disobey not the commands they receive from Allah, but do that which they are commanded.) meaning, whatever Allah commands them, they rush to obey Him, without delay for even a twinkling of an eye. They are able to fulfill the command; they are called Az-Zabaniyah, meaning, the keepers and guards of Hell, may Allah give us shelter from them.