The strongest form of this objection is that some Quranic sentences do not match the simple grammatical patterns later students expect. The strongest answer is that Arabic grammar is not a set of English-like rules imposed on the Quran; it is a description of the actual speech of the Arabs, with the Quran at its center.
Why the criticism can sound persuasive
The objection is not silly. A reader sees a singular expression, then a plural pronoun, or sees a word in a case that looks unexpected. Critics then say: if this were divine speech, it should not need explanation by grammarians and commentators.
Examples often raised include Quran 2:17, 4:162, 5:69, and 20:63. The argument is that these are not merely difficult verses, but grammatical breaks. If so, they would be serious. A book claiming divine origin cannot contain bad Arabic.
What happens in Quran 2:17
Their example is like that of one who kindled a fire; when it lit up what was around him, Allah took away their light and left them in darkness, so they do not see.
Quran 2:17
The verse is speaking about a group - the hypocrites - and gives their collective example through the image of "one who kindled a fire." Arabic often uses a singular representative figure for a whole class, then returns to the group being discussed. English does this too: "The person who cheats people loses their trust." That is not a mistake; it is a shift from the individual image to the group represented by it.
In Arabic rhetoric this is even more natural. The singular makes the parable vivid: one man lighting a fire in darkness. The plural then reminds the listener that the parable applies to many people. The verse is not confused about its subject; it moves deliberately between the picture and the people pictured.
Grammar is wider than schoolbook agreement
Later grammar books summarize common patterns. They do not exhaust the language. The earliest grammarians built their rules from the Quran, ancient Arab poetry, Bedouin speech, and transmitted recitation. So when a verse has a less common construction, the first question is not, "Which modern rule did it break?" but "Is this construction known in Arabic?"
This is why classical scholars did not see themselves inventing desperate workarounds. They were analyzing real Arabic. For example, the accusative in Quran 4:162 - "wal-muqimeena al-salah" - is commonly explained as a known accusative of praise. Quran 5:69, where "al-sabi'un" appears nominative after "inna," has recognized syntactic explanations, and its contrast with Quran 2:62 shows that the Quran is not unaware of the expected form. Quran 20:63 is also discussed through established dialectal usage and variant grammatical analysis in the recitations.
One may disagree with a particular parsing, but the mere existence of grammatical discussion is not evidence of error. Advanced Arabic, like advanced Latin or Greek, often requires analysis. Difficulty is not the same as defect.
What this does and does not establish
What the objection establishes is modest: some Quranic passages are not beginner-level Arabic, and some constructions require knowledge of rhetoric, dialect, ellipsis, emphasis, or case variation. That is fair.
What it does not establish is that the Quran contains grammatical errors. To prove that, a critic would need to show that a construction is impossible in sound Arabic, not merely unexpected under a simplified rule. The famous examples do not meet that standard.
The Quran was first heard by people whose strongest public weapon against Prophet Muhammad (PBUH) was language. They accused him of many things, but the Quran's Arabic force and beauty were undeniable even to its opponents. These verses are not blemishes in divine speech; they are places where the depth of Arabic outgrows a classroom shortcut.