Tafsir of Ar-Rahman 55:19-23

{ Maraja al-baḥrayni }: He sent forth the salt sea and the fresh sea, adjacent and meeting, with no separation between the two waters to the naked eye.

{ Baynahumā barzakhun }: A barrier from the power of Allah Almighty.

{ Lā yabghiyān }: They do not transgress their limits, nor does one encroach upon the other by mixing.

{ Yakhruju minhumā al-lu’lu’u wa-l-marjān }: It is read as yakhruju (it comes out), yukhraju (it is brought out), akhraja (He brought out), kharaja (it came out), and yukhriju (He brings out)—meaning Allah, the Almighty and Exalted.

• Al-lu’lu’: Pearls.
• Al-marjān: These red beads, which is coral (al-basadh). It is also said: Al-lu’lu’ are the large pearls, and al-marjān are the small ones.

If you ask: Why did He say "from both of them" (minhumā) when they only come out of the salt sea?

I reply: Since they meet and become like one thing, it is permissible to say they come out of both, just as it is said they come out of the sea, even though they do not come out of the entire sea, but only from a part of it. You say, "I left the city," even though you only left one of its districts, or even just one house among its houses. It is also said: They only emerge from the confluence of the salt and the fresh.