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. (25:53)

Or, Who has made the earth firm to live in; made rivers in its midst; set thereon mountains immovable; and made a separating bar between the two bodies of flowing water? (can there be another) god besides God? Nay, most of them know not. (27:61)

Nor are the two bodies of flowing water alike,- the one palatable, sweet, and pleasant to drink, and the other, salt and bitter. Yet from each (kind of water) do ye eat flesh fresh and tender, and ye extract ornaments to wear; and thou seest the ships therein that plough the waves, that ye may seek (thus) of the Bounty of God that ye may be grateful. (35:12)

He has let free the two bodies of flowing water, meeting together: (55:19)

Then which of the favours of your Lord will ye deny? (55:21)