55:20
بَيْنَهُمَا بَرْزَخٌۭ لَّا يَبْغِيَانِ ٢٠
Saheeh International
Between them is a barrier [so] neither of them transgresses.
Tafsir of "Ibn Kathir" (English)
Between them is a barrier which none of them can transgress.meaning, He has placed a barrier of land between these two types of waters, so that they do not transgress upon each other, which would spoil the characteristics they were created with.