He sends down water from the sky which flows in valleys according to its program, so that the torrent bears (on its surface) a swelling foam, and from that which they melt in fire for making ornaments or things (of utility, rises) a foam similar to it, thus Allah strikes (a comparison between) the truth and the falsehood. So as for the foam it passes away as useless froth and as for that which is useful to mankind, it remains in the earth. Thus does Allah (explain by) striking examples.