Surah Al-Furqan (The Criterion), Verse 53

وَهُوَ الَّذِیْ مَرَجَ الْبَحْرَیْنِ هٰذَا عَذْبٌ فُرَاتٌ وَّهٰذَا مِلْحٌ اُجَاجٌ وَجَعَلَ بَیْنَهُمَا بَرْزَخًا وَّحِجْرًا مَّحْجُوْرًا ۟

Wa Huwal lazee marajal bahraini haazaa 'azbun furaatunw wa haazaa milhun ujaaj; wa ja'ala bainahumaa barzakhanw wa hijran mahjooraa

“It is He Who has let free the two bodies of flowing water: One palatable and sweet, and the other salt and bitter; yet has He made a barrier between them, a partition that is forbidden to be passed.”

Quran 25:53 (Yusuf Ali Translation)