Tafsir of Ar-Rahman 55:19

He has Maraja the two seas, or let them loose, according to Ibn Abbas. Allah's statement,

يلتقيان

(meeting together), Ibn Zayd said, "He prevents them from meeting by the dividing barrier He placed between them to separate them.'' The two seas are the fresh and salty waters, the former coming from running rivers. We discussed this topic in Surah Al-Furqan when explaining Allah's statement;

وهو الذى مرج البحرين هذا عذب فرات وهذا ملح أجاج وجعل بينهما برزخا وحجرا محجورا

And it is He Who has let free the two seas: one palatable and sweet, and the other salty and bitter; and He has set a barrier and a complete partition between them. (25:53) Allah said,

بينهما برزخ ﻻ يبغيان