Quran 13:17

أَنزَلَ مِنَ ٱلسَّمَآءِ مَآءً۬ فَسَالَتۡ أَوۡدِيَةُۢ بِقَدَرِهَا فَٱحۡتَمَلَ ٱلسَّيۡلُ زَبَدً۬ا رَّابِيً۬ا‌ۚ وَمِمَّا يُوقِدُونَ عَلَيۡهِ فِى ٱلنَّارِ ٱبۡتِغَآءَ حِلۡيَةٍ أَوۡ مَتَـٰعٍ۬ زَبَدٌ۬ مِّثۡلُهُ ۥ‌ۚ كَذَٲلِكَ يَضۡرِبُ ٱللَّهُ ٱلۡحَقَّ وَٱلۡبَـٰطِلَ‌ۚ فَأَمَّا ٱلزَّبَدُ فَيَذۡهَبُ جُفَآءً۬‌ۖ وَأَمَّا مَا يَنفَعُ ٱلنَّاسَ فَيَمۡكُثُ فِى ٱلۡأَرۡضِ‌ۚ كَذَٲلِكَ يَضۡرِبُ ٱللَّهُ ٱلۡأَمۡثَالَ ١٧

He sends down water from the sky, causing the valleys to overflow, then the rapids produce abundant foam. Similarly, when they use fire to refine metals for their jewelry or equipment, foam is produced. ALLAH thus cites analogies for the truth and falsehood. As for the foam, it goes to waste, while that which benefits the people stays close to the ground. ALLAH thus cites the analogies.