Allah sends down water from the heavens and the river-beds 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 (the truth) through examples.