We have appointed none but angels as the keepers of the Fire, and We have not made their number but as a trial for the unbelievers so that those who have been endowed with the Book will be convinced and the believers' faith will increase, and neither those who have been endowed with the Book nor the believers will fall into any doubt. As for those in whose hearts there is a sickness as well as the unbelievers, they will say: “What did Allah aim at by this strange parable?” Thus does Allah let whomsoever He pleases to go astray, and directs whomsoever He pleases to the Right Way. And none knows the hosts of your Lord but He. (And Hell has only been mentioned here) that people may take heed.