Surely Allah is not ashamed to set forth any parable-- (that of) a gnat or any thing above that; then as for those who believe, they know that it is the truth from their Lord, and as for those who disbelieve, they say: What is it that Allah means by this parable: He causes many to err by it and many He leads aright by it! but He does not cause to err by it (any) except the transgressors,

And We will draw forth from among every nation a witness and say: Bring your proof; then shall they know that the truth is Allah's, and that which they forged shall depart from them.