Tafsir of Ghafir 40:23

A compelling, manifest proof. Regarding this, it is said that it refers to the same as what was meant by "the signs," and the difference between the two descriptions is treated as equivalent to the difference between two distinct entities, thus the second is conjoined to the first. It is also said that it refers to a portion of his signs that possess particular significance, such as the staff, and it is conjoined to the former to magnify its status, just as Gabriel and Michael, peace be upon them, are conjoined to [the mention of] the angels.

This has been critiqued by the observation that such a construction only occurs when the second [term] is specified by a proper noun or similar; as for it being indefinite, that is debatable. Al-Tabarsi narrated that what is meant by "the signs" are the proofs of monotheism, and by "authority," the miracles indicating his prophethood, peace be upon him. It is also said that the "signs" are the miracles, and the "authority" is what he was granted, peace be upon him, of sacred strength, its manifestation being considered in light of the appearance of its effects, such as undertaking the call [to God] without hesitation. Isa read it as sultan (with a damma on the lam).