He sends down water from the cloud, then watercourses flow (with water) according to their measure, and the torrent bears along the swelling foam, and from what they melt in the fire for the sake of making ornaments or apparatus arises a scum like it; thus does Allah compare truth and falsehood; then as for the scum, it passes away as a worthless thing; and as for that which profits the people, it tarries in the earth; thus does Allah set forth parables.