Tafsir of Az-Zumar 39:28

(A Quran in Arabic) is a circumstantial qualifier (ḥāl) for "this," and the reliance in it is upon the descriptor, which is "in Arabic." Otherwise, "a Quran" is an inert noun that is not fit to be a circumstantial qualifier, and it is also identical to the one it describes, so its state would not be manifest. Therefore, the circumstantial qualifier in reality is "in Arabic," while "a Quran" serves as a preface. A parallel to this is: "Zayd came as a righteous man." It has been said that this is equivalent to saying "truly in Arabic."

It is also permitted that it be accusative governed by an implicit verb, with the estimated meaning of "I mean," "I specify," "I praise," or similar; or that it be the object of the verb "they may remember." This, however, is as you see it [to be unlikely].

(Free from crookedness): meaning there is no inconsistency in it in any aspect whatsoever. This is more eloquent than "upright" (mustaqīm), for "crookedness" (‘iwaj) is an indefinite noun occurring in a negative context due to the meaning inherent in "free from" (ghayr). Uprightness could be allowed in one aspect but not another, whereas the negation of any accompaniment of crookedness necessitates the negation of being described by it, which is by way of priority more eloquent than "not crooked."

"Crookedness" (‘iwaj), with a kasra, is said of that which is perceived by thought and insight; "crookedness" (‘awaj), with a fatḥa, is said of that which is perceived by the senses. The former was chosen to indicate that it has reached a limit where the intellect cannot perceive any crookedness in it, let alone the senses. The remainder of the discussion has passed in Surah al-Kahf.

It is said that the intent by "crookedness" is doubt and confusion. This has been narrated from Mujahid, and they cited the poet's verse: "And there has come to you a certainty, free from crookedness, from the God, and a saying not belied." There is no proof in this that "crookedness" means "doubt," for the crookedness of certainty is doubt, inevitably. The argument regarding the mode of deduction is that the poet understood this meaning from the verse because it is an act of quoting (iqtibās). If a fluent speaker understands it with the validity of metaphorical usage, then claiming it is a forced interpretation is apparent, because it is not clear that he quoted it from this verse. Even if granted, it would be susceptible to what "crookedness" can be interpreted as in the arrangement in which there is no crookedness.

It is sometimes said: The intent of those who said "meaning there is no confusion or doubt in it" is the negation of certain types of disorder. To this effect is what is narrated from Uthman ibn Affan, that he said: Meaning it is neither unstable nor contradictory. It has also been said: Meaning it is free from grammatical error. Al-Daylami recorded in Musnad al-Firdaws from Anas from the Prophet, may Allah bless him and grant him peace, that he said: "Free from crookedness—not created." Perhaps, if the report is authentic, it is an interpretation by way of necessary implication, so reflect upon it.

(That they may be God-fearing): another rationale dependent upon the first.