التفسير التبليغي
(Between them is a barrier, so they do not transgress [upon one another].) (20)
(Between them is a barrier, so they do not transgress [upon one another]): meaning, neither transgresses upon the other. The rivers flow with their sweet water, and the seas remain with their salty water. Between them is a barrier, so this does not transgress upon that; this is separated from that.
(Between them is a barrier): which is the dry land. (so they do not transgress [upon one another]): meaning, neither of them transgresses upon the other. If Allah Almighty had willed, He could have unleashed the seas, causing them to overflow and inundate the earth.
(Between them is a barrier): meaning, a separator. (so they do not transgress [upon one another]): meaning, they do not mix, thereby altering their taste.
There is a barrier that separates every two seas, and it moves between them.
The three water masses (river water, sea water, and estuary water) do not mix in terms of salinity and freshness. River waters are very fresh, sea waters are very salty, and the waters in the estuary region are a mixture of salinity and freshness, forming a transitional zone between the sea and the river.
The origin of *al-baghy* (transgression) is: overstepping limits, injustice, and oppression.
The power of Allah Almighty prevents them from mixing.
Source: التفسير التبليغي