It spares not (any sinner), nor does it leave (anything unburnt)!
Burning and blackening the skins!
Over it are nineteen (angels as guardians and keepers of Hell).
And We have set none but angels as guardians of the Fire. And We have fixed their number (19) only as a trial to the disbelievers, in order that the people of the Scripture (Jews and Christians) may arrive at a certainty [that this Qur'an is the truth as it agrees with their Books regarding the number (19) which is written in in the Taurat (Torah) and the Injil (Gospel)] and that the believers may increase in Faith (as the Qur'an is the truth), and that no doubt may be left for the people of the Scripture and the believers, and that those in whose hearts is a disease (of hypocrisy) and the disbelievers may say "What Allah intends by this (curious) example?" Thus Allah leads astray whom He wills and guides whom He wills. And none can know the hosts of your Lord but He. And this (Hell) is nothing else than a (warning) reminder to mankind."
(Surah 74: Al-Muddaththir (The One Enveloped); verses 27-31)