allah sends down water from the heavens and the riverbeds flow each according to its measure and the torrent carries along a swelling scum. in like manner from that metal which they smelt in the fire to make ornaments and utensils there arises scum like it. thus does allah depict truth and falsehood. as for the scum it passes away as dross but that which benefits mankind abides on the earth. thus does allah explain through examples.
أنزل من السماء ماء فسالت أودية بقدرها فاحتمل السيل زبدا رابيا ومما يوقدون عليه في النار ابتغاء حلية أو متاع زبد مثله كذلك يضرب الله الحق والباطل فأما الزبد فيذهب جفاء وأما ما ينفع الناس فيمكث في الأرض كذلك يضرب الله الأمثال