"Those in the Fire will say to the keepers of Hell, 'Pray to your Lord to lighten for us the penalty for a day (at least).' They will say, 'Did there not come to you your messengers with clear signs?' They will say, 'Yes.' They will reply, 'Then pray as you like. But the prayer of those without faith is not but in error.'"
[Ghafir, 40: 49-50]
"O you who believe, save yourselves and your families from a fire whose fuel is men and stones, over which are (appointed) angels, stern and severe, and who do not disobey Allah in what He orders them and who do precisely what they are commanded."
[at-Tahreem, 66: 6]
"Over it are nineteen. And We have not made the guardians of the Fire except angels. And We have made their number only as a trial for the unbelievers - in order that the People of the Book may be certain and that the believers may increase in faith, and so that the People of the Book and the believers would not doubt, and that those in whose hearts is a disease and the unbelievers would say, 'What example does Allah intend by this?' Thus does Allah leave to stray whom he pleases and guides whom He pleases. And none can know the soldiers of your Lord except He. And this is nothing other than a warning to mankind."
[Muddaththir, 74: 30-31]
"They will cry out, 'O Malik, let your Lord put an end to us.' He will say, "Surely, you will stay (as you are).'"
[adh-Dhukhrub, 43: 77]
Samurah (radiAllahu anhu) narrated that the Prophet (salAllahu alayhi wasalam) said: "Last night I saw [in a dream] two men coming to me. One of them said, 'The one who lights the fire is Malik, the gatekeeper of Hell; I am Jibreel, and this is Mika'eel.'"
Ibn Abbas (radiAllahu anhu) related: "The Prophet (salAllahu alayhi wasalam) said, 'On the night of my ascent to Heaven. I saw Musa (who was a tall, brown, curly-haired man) as if he was one of the men of the Shan'awah tribe. Then I saw 'Isa, a man of medium height, of moderate complexion inclined to the red and white colors, and of lank hair. I also saw Malik, the gatekeeper of the Hellfire.'"