Key Verses

1. 23:100Al-MuminunCommand
   لَعَلِّيٓ أَعۡمَلُ صَٰلِحٗا فِيمَا تَرَكۡتُۚ كَلَّآۚ إِنَّهَا كَلِمَةٌ هُوَ قَآئِلُهَاۖ وَمِن وَرَآئِهِم بَرۡزَخٌ إِلَىٰ يَوۡمِ يُبۡعَثُونَ
   That I may do right in that which I have left behind! But nay! It is but a word that he speaketh; and behind them is a barrier until the day when they are raised.
   In context

   Perhaps I will do good actions when I return to it. Never. The matter is not as you requested. It is only a statement he is uttering. If he were to return to the worldly life, he would not fulfil what he promised. These people who have died will remain in a barrier between the world and the afterlife until the Day of Resurrection and rising.

2. 25:53Al-FurqanWarning
   ۞وَهُوَ ٱلَّذِي مَرَجَ ٱلۡبَحۡرَيۡنِ هَٰذَا عَذۡبٞ فُرَاتٞ وَهَٰذَا مِلۡحٌ أُجَاجٞ وَجَعَلَ بَيۡنَهُمَا بَرۡزَخٗا وَحِجۡرٗا مَّحۡجُورٗا
   And He it is Who hath given independence to the two seas (though they meet); one palatable, sweet, and the other saltish, bitter; and hath set a bar and a forbidding ban between them.
   In context

   It is Allah, may He be glorified, who merged the water of the two bodies of flowing water. He mixed the sweet and the salty, and put a barrier and dividing line between them that prevents them from intermingling.

3. 55:20Ar-RahmanNeutral
   بَيۡنَهُمَا بَرۡزَخٞ لَّا يَبۡغِيَانِ
   There is a barrier between them. They encroach not (one upon the other).
   In context

   Between them is a barrier that prevents each one of them from transgressing over the other so that the sweet remains sweet and the salty remains salty.