He sends down rain from the sky, causing the valleys to flow, each according to its capacity. The currents then carry along rising foam, similar to the slag produced from metal that people melt in the fire for ornaments or tools. This is how Allah compares truth to falsehood. The residue is then cast away, but what benefits people remains on the earth. This is how Allah sets forth parables.
-Quran 13:17
at 18:52
