Tafsir of An-Nazi'at 79:37

As for the phrase "As for him who transgressed," it is the answer to the "when" (idha)—treating it as conditional rather than adverbial. This is permitted, following the structure of His saying, the Exalted: "Then if there comes to you guidance from Me" (Qur'an 2:38), and your saying, "When the tribe of Tamim comes to you, as for the disobedient, insult him, and as for the obedient, honor him." Abu Hayyan preferred this.

It has been said that its answer is omitted, as if it were said: "When it (the Great Catastrophe) arrives, that which cannot be described will occur," and His saying, "As for him who transgressed," is an elaboration of that omitted part. There is obscurity in treating it as the answer, although it is a sound view. However, there is no obscurity in the former once it is established that it is correct to say: "When it arrives, then indeed the transgressor's abode is Hell, and the other's resting place is Paradise." The addition of "as for" (amma) serves only to increase emphasis and to realize the sequence and fixity in any given scenario.

It has also been said that it is omitted due to the indication of what precedes it—the implication being: "Deeds will be manifested and scrolls will be unfolded," or "Man will remember what he exerted,"—or due to the indication of what follows it—the implication being: "The observers will be divided into two groups." But that is not strong.

That is to say: As for the one who acted haughtily, rebelled against obedience, and exceeded the limits in disobedience until he committed disbelief.