Tafsir of Al-A'raf 7:158

{Indeed, I am the Messenger of Allah to you all} It is said: Every messenger was sent specifically to his own people, while Muhammad (may Allah bless him and grant him peace) was sent to all of mankind and all of the jinn. "All" (jamīʿan) is in the accusative case as a state (ḥāl) derived from "to you" (ilaykum).

If you ask: What is the grammatical position of {to whom belongs the dominion of the heavens and the earth}? I say: The best interpretation is that it is in the accusative case due to an implied verb, "I mean" (aʿnī), which is what is known as the accusative of praise (al-naṣb ʿalā al-madḥ). It is also permissible for it to be in the genitive case as an adjective (waṣf), even if the phrase "to you" (ilaykum) intervenes between the adjective and the described noun.

{To you all} and the statement {There is no god but He} serve as a substitute (badal) for the relative clause (ṣilah) which is "to whom belongs the dominion of the heavens and the earth." Likewise, {There is no god}. In {There is no god but He} is an explanation of the preceding sentence, because whoever possesses the dominion of the world is the true God. In {He gives life and causes death} is an explanation of His exclusivity in divinity, for no one is capable of giving life and causing death except Him.

{And His words} Meaning what was revealed to him and to the messengers who preceded him from His scriptures and revelation. It has been recited in the singular: {And His word} (wa-kalimatihi), which refers to the Quran, or it intends the genus of what He has spoken.

From Mujahid: He intended Jesus, son of Mary. It is also said: It is the word from which Jesus and all of creation came into being, which is His saying: "Be" (kun). Jesus was called the "Word of Allah" and singled out by this name because there was no cause for his existence other than the Word, and he was not from a drop of semen.

{That you might be guided} Meaning: intending that you be guided.

If you ask: Why was it not said, "So believe in Allah and in me," after his saying: {Indeed, I am the Messenger of Allah to you all}? I say: He shifted from the pronoun to the explicit noun to allow the attributes that were applied to him to follow, and because of the rhetorical excellence found in the method of shifting (iltifāt). It is also to make it known that the one who must be believed in and followed is this specific person—the Unlettered Prophet who believes in Allah and His words—whoever he may be, whether it is I or someone else, in order to demonstrate fairness and avoid self-centered bias.