Surah Al-Waqi'ah Verse 70

5253 The mystery of the two streams of water, one sweet and the other salt, constantly mingling, and yet always separate, is referred to more than once. The never-ending circuit is established by streams and rivers mingling with the ocean, the ocean sending forth mists and steam through a process of evaporation which forms clouds, and the clouds by condensation pouring forth rain to feed the streams and rivers again: see notes 3111-3112 to 25:53, and n. 5185 to 55:19, and the further references given there.