We have assigned only angels as keepers of the Fire , and We have made their number merely a stumbling block for the faithless , and so that those who were given the Book may be reassured , and the faithful may increase in [ their ] faith , and so that those who were given the Book and the faithful may not be in doubt , and so that the faithless and those in whose hearts is a sickness may say , ‘ What did Allah mean by this description ? ’ Thus does Allah lead astray whomever He wishes and guides whomever He wishes .