Al-Muddathir - 74:31

And We have not made the wardens of the fire others than angels, and We have not made their number but as a trial for those who disbelieve, that those who have been given the book may be certain and those who believe may increase in faith, and those who have been given the book and the believers may not doubt, and that those in whose hearts is a disease and the unbelievers may say: What does Allah mean by this parable? Thus does Allah make err whom He pleases, and He guides whom He pleases, and none knows the hosts of your Lord but He Himself; and this is naught but a reminder to the mortals.

And We have set none but angels as Guardians of the Fire; and We have fixed their number only as a trial for Unbelievers,- in order that the People of the Book may arrive at certainty, and the Believers may increase in Faith,- and that no doubts may be left for the People of the Book and the Believers, and that those in whose hearts is a disease and the Unbelievers may say, "What symbol doth Allah intend by this?" Thus doth Allah leave to stray whom He pleaseth, and guide whom He pleaseth: and none can know the forces of thy Lord, except He and this is no other than a warning to mankind.

We have appointed only angels to be wardens of the Fire, and their number have We made to be a stumbling-block for those who disbelieve; that those to whom the Scripture hath been given may have certainty, and that believers may increase in faith; and that those to whom the Scripture hath been given and believers may not doubt; and that those in whose hearts there is disease, and disbelievers, may say: What meaneth Allah by this similitude? Thus Allah sendeth astray whom He will, and whom He will He guideth. None knoweth the hosts of thy Lord save Him. This is naught else than a Reminder unto mortals.