Tafsir of Al-Furqan 25:35

"And We certainly gave Moses the Book..." (and so on). This is an inaugural sentence presented to reinforce the consolation, the promise of guidance, and the promise of victory mentioned previously in His saying, "And sufficient is your Lord as a guide and a helper," by recounting what transpired between those mentioned among the prophets—peace be upon them—and their peoples, in a summary account sufficient for the intended purpose.

The lam (in la-qad) is situated in the place of an oath response, meaning: "And by Allah, the Exalted, We have indeed given Moses the Torah," i.e., We revealed it to him in the hereafter (meaning finally/conclusively). It is also said that what is meant by "the Book" is wisdom and prophethood, though its distance [from the intended meaning] is not hidden.

"And We appointed with him..." the circumstantial adverb (the prepositional phrase) is connected to "appointed." His saying, "his brother," is the first direct object of the verb, and His saying, "Aaron," is a substitute (badal) for "his brother" or an explanatory appositive (‘atf bayan) for it. His saying, "as a minister," is the second direct object of the verb.

The meaning of "minister" (wazir) has already been discussed. This does not contradict His saying, "And We gifted him his brother Aaron as a prophet," because even if he was a prophet, the Sharia (law) was for Moses—peace be upon him—and Aaron was a follower of him in it, just as a minister follows his sovereign.