(And he is in the highest horizon)

Meaning the upper region of the sky that faces the observer. Its origin is "the side." What the astronomers mention is a technical definition, and it is divided according to them into real and non-real, as detailed in its proper place. Ibn al-Mundhir recorded from Ibn Abbas that the intended meaning here is the place where the sun rises. In the same vein is the saying of al-Hasan: "It is the horizon of the east."

The sentence is in the position of a circumstantial qualifier (hal) for the subject of istawa (he rose/leveled). Al-Farra and al-Tabari said: "It is a conjunction to the hidden pronoun in istawa, and it refers to the Prophet, may Allah bless him and grant him peace, just as 'that' refers to Gabriel, peace be upon him." The reverse is also considered permissible. The prepositional phrase is connected to istawa. It involves conjunction to the nominative pronoun without separation, which is the position of the Kufans, although the meaning does not support this according to the majority.