Tafsir of Al-An'am 6:58

(Say, if I had)—that is, within my power and ability—(what you are impatient for of the punishment, the matter would have been settled between me and you)—that is, by the punishment descending upon you as a consequence of your impatience. The construction of the verb in the passive voice [ qudiya - was settled] contains an implication—which is not hidden—that the agent is Allah, may His Majesty be glorified, as well as an expression of the gravity of the matter and an observance of proper etiquette.

Al-Zamakhshari and those who followed him said: The meaning is, "If that were within my power, I would have destroyed you immediately, out of anger for the sake of my Lord—mighty and majestic is He—and indignation at your denial of Him, and I would have been rid of you quickly." However, the context does not support this. Similarly, interpreting "what you are impatient for" as the requested miracles, and "the matter being settled" as the establishment of the Hour, is not supported.

(And Allah is most knowing of the wrongdoers)—that is, of their state and that they are deserving of respite by way of istidraj (gradual leading to destruction) in order to intensify their punishment. For this reason, the matter was not delegated to me, and the decree was not for the hastening of the punishment. This sentence confirms what the conditional sentence (the imtinaiyyah) conveyed—namely, the negation that the matter of punishment was delegated to him (peace and blessings be upon him), which entails the negation of the matter being settled [by him], and it serves as a justification for it.

It has been said: It carries the meaning of a rectification, as if it were said: "If I had the power, I would have destroyed you, but Allah the Exalted is more knowing of who is to be destroyed and who is not, and He has wisdom in not granting the power to do so." Regardless, there is no need to assume the omission of a genitive (mudaf), as some have claimed—with the estimation being "the time of the punishment of the wrongdoers"—for that is as you see it [to be weak]. And Allah the Exalted knows best.