Tafsir of Al-Fajr 89:15

His saying—Exalted is He—{As for man, when...} is connected to what precedes it, as if it were said: "Indeed, your Lord is in wait" for the sake of the Hereafter, and He does not seek—Mighty and Majestic is He—aught but striving for it. As for man, nothing concerns him except the worldly life and its pleasures; if he attains something of it, he is pleased, and if not, he is disgruntled. It would have been more befitting that nothing concern him except what Allah—Mighty and Majestic is He—seeks, and that his state not be such. It is also said that it is connected to it and branching from it, in the sense that man is inevitably held to account, for he is caught between wealth that ruins him and invites arrogance and pride in the worldly life, and poverty that he cannot endure, causing him to disbelieve due to impatience and the uttering of what is inappropriate—and this is as you see.

{When his Lord tests him}—that is, treats him with the treatment of one who tests him—{with honor} and ease, to see whether he will be grateful or not. The fa in His saying—Exalted is He—{so He honors him and blesses him} is explanatory, for honoring and blessing are the very essence of what is meant by "testing." Since honoring and blessing are in the ruling of a single thing, He sufficed with saying "He honored me" in His saying—Exalted is He—{and says, "My Lord has honored me,"} without adding "and blessed me" to it. This sentence is the predicate for the subject, which is "man," and the fa is there because of the conditional meaning inherent in "as for" (amma).

The adverb—I mean "when"—is connected to "says," with the intention of postponement. The fa does not prevent this, as stated by al-Zamakhshari and other early grammarians, followed by those who came after them like Abu Hayyan, al-Samin, and al-Safaqsi, along with a vast number of exegetes. This is, as Shihab said, the truth from which there is no turning away. Al-Radi and those who followed him, such as al-Badr al-Damamini in Sharh al-Mughni, differed with them, saying that it is only permissible to move what comes after the fa to before it if the moved element is the separator between "as for" (amma) and the fa due to the objectives served by such movement. If there is another separator there, the movement of anything else is forbidden; thus, "As for Zayd, your food, he eats" is forbidden, even if "As for your food, Zayd eats" is permissible. They argued that because they committed to the omission [of the verb], the entry of its particle upon the fa of the response became necessary, which is disliked, so necessity compelled separating them with something from what follows the fa, and the single separator is sufficient, so it is obligatory to limit it to that.

Al-Chalabi, the commentator of al-Mutawwal, claimed that this is a matter of consensus, and he rejected the aforementioned parsing by the exegetes, labeling it an error. The correct view, in his opinion, is to make the adverb connected to a suppressed element, which is in reality the subject; the estimation being: "As for the state of man, when..." Thus, the adverb is part of the separated clause and is not a second separator, similar to your saying, "As for Zayd's kindness to the poor, it is good." The objection to his estimation is that it is not valid for the sentence "he says" to be the predicate of "the state" except with forced interpretation, such as the verb being interpreted as a verbal noun (masdar), even if the particle an (that) is not present with it in the wording, as was said in: Hearing about al-Mu'aydi is better than seeing him. This is a flight from the clouds to the water spout. Abu al-Baqa' went to the view that "when" is conditional and His saying—Exalted is He—{he says} is its response, and the conditional sentence is the predicate of "man," which necessitates an omission before "says." It has been said that this is a necessity.