Or [else, their deeds are] like the depths of darkness upon an abysmal sea, made yet more dark by wave billowing over wave, with [black] clouds above it all: depths of darkness, layer upon layer, [so that] when one holds up his hand, he can hardly see it: for he to whom God gives no light, no light whatever has he! (Quran 24:40)
Could, then, one whose bosom God has opened wide with willingness towards self-surrender unto Him, so that he is illumined by a light [that flows] from his Sustainer, [be likened to the blind and deaf of heart]? Woe, then, unto those whose hearts are hardened against all remembrance of God! They are most obviously lost in error!
We have thus revealed a Spirit to you [Prophet] by Our command: you knew neither the Scripture nor the faith, but We made it a light, guiding with it whoever We will of Our servants. You are indeed guiding to the straight path. (Quran 42:52)