Tafsir of Ar-Rahman 55:17

Lord of the two easts and Lord of the two wests.

It has been recited: "Lord of the two easts and Lord of the two wests" in the genitive case (jarr), as a substitute for "your Lord" (rabbikumā). He intended by this the two easts of summer and winter, and their two wests.

He released the two seas, meeting [side by side]. Between them is a barrier [so] neither transgresses. So which of the favors of your Lord would you deny? From both of them emerge pearl and coral. So which of the favors of your Lord would you deny?