Ar-Ra'd 13:17 انزل من السماء ماء فسالت اودية بقدرها فاحتمل السيل زبدا رابيا ومما يوقدون عليه في النار ابتغاء حلية او متاع زبد مثله كذالك يضرب الله الحق والباطل فاما الزبد فيذهب جفاء واما ما ينفع الناس فيمكث في الارض كذالك يضرب الله الامثال ١٧

He sends down water (rain) from the sky, and the valleys flow according to their measure, but the flood bears away the foam that mounts up to the surface - and (also) from that (ore) which they heat in the fire in order to make ornaments or utensils, rises a foam like unto it, thus does Allâh (by parables) show forth truth and falsehood¹. Then, as for the foam it passes away as scum upon the banks, while that which is for the good of mankind remains in the earth. Thus Allâh sets forth parables (for the truth and falsehood, i.e. Belief and disbelief).