Tafsir of Al-Mu'minoon 23:45

(Then We sent Moses and his brother Aaron with Our signs), meaning the well-known signs, which are the nine signs; the detailed discussion regarding them and what has been said about them has already preceded. (And Aaron) is an appositive (badal) or an explanatory attribute (‘atf bayan), and mention is made of his brotherhood to Moses, peace be upon them both, to indicate his subordination to him in the mission. (And a manifest authority), meaning a clear proof that manifests the truth. According to a group, what is intended by this is the staff. It is mentioned individually despite being included within the signs because of its unique characteristics, to the point that it became as if it were something else. It is also permissible that "the signs" is what is intended by it, and the conjunction is that of two terms sharing the same referent (ittihad al-masdaq) despite the difference in their literal meanings, similar to conjoining an adjective to an adjective while the essence remains one; an analogy for this has passed just before. Or, it may be of the category of your saying: "I passed by the man and the blessed soul," where a 'manifest authority' is abstracted from the signs themselves and conjoined to them. It is brought in the singular form because it is originally an infinitive (masdar), or because of the unity of the intended meaning.

Al-Hasan stated that what is meant by "the signs" are the religious obligations, and by "the manifest authority" are the miracles. Abu Hayyan said: It is permissible that "the signs" refers to the miracles themselves, and "the manifest authority" refers to the nature of their indication; for although they share with the signs of the other prophets, peace be upon them, the fundamental indication of truthfulness, they distinguish themselves from them in the strength of that indication. This, as you can see, is a view. It is also possible to say: What is meant by the "authority" is the dominance of Moses, peace be upon him, in argumentation and reasoning regarding the Creator, Exalted and Majestic is He, and his strength of heart and boldness.