There are grammar mistakes in the Qur'an!
This is indeed a very strange allegation!
The grammar of the Arabic language is largely founded on the Qur'an and was not put down in writing until well over a hundred years after the Qur'an was revealed. The Classical Arabic language became a language we can talk about as having a fixed grammar largely because of the Qur'an. Dictionaries and grammar books were first written to preserve the language of the Qur'an and the hadiths from the changes to the Arabic language that were happening as a result of the sudden growth of the Islamic Caliphate into new populations stretching from (what is now) Pakistan to Portugal. My own pocket grammar book uses quotes from the Qur'an as its proofs for most of its 500 grammar rules.
One further thing I find strange is that this should come from Christians. The reason is that the New testament is all written in a form of slang Greek called "Demotic Greek" . This was a corrupted popular form of classical Greek which paid little heed to the grammar rules. Any grammatical analysis of the bible would be hard pressed to find a sentence without a grammar deviation from the rules of classical Greek.
Nevertheless, the points raised may as well be explained:
Muslims claim the Qur'an not just to be a human literary masterpiece, but a divine literary miracle. But this claim does not square with the facts. For the Qur'an which we have in our hands contains obvious grammatical errors which is plain to see for all who know Arabic.
The First Error
In 5:69 "Surely they that believe, and those of Jewry, and the Sabaeans, and the Christians, whosoever believes in God and the Last Day, and works righteousness - no fear shall be on them, neither shall they sorrow." (Arberry)
"Innal-laziina 'aamanuu wal-laziina haaduu was-Saabi'uuna wan-Nasaaraa man 'aamana bilaahi wal-Yawmil-'Aakhiri wa 'amila saali-hanfalaa khaw-fun 'alay-him wa laa hum yah-zanuun."
There is a grammatical error in the above verse. The word Saabi'uuna has been declined wrongly. In two other verses, the same word, in exactly the same grammatical setting was declined correctly.
2:62 "Innal-laziina 'aamanuu wal-laziina haaduu wan-Nasaaraa was-Saabi'iina ..."
22:17 "Innal-laziina 'aamanuu wal-laziina haaduu was-Saabi'iina wan-Nasaaraa ..."
You notice that the word was written Saabi'uuna in 5:69 and was written Saabi'iina in 2:62 and 22:17. In the last two verses the word was declined correctly because the word inna in the beginning of the sentence causes a form of declension called "nasb" (as in cases of accusative or subjunctive) and the "yeh" is the "sign of nasb". But the word Saabi'uuna in 5:69 was given the 'uu, waw which is the sign of "raf'a" (as in cases of nominative or indicative). This then is an obvious grammatical error.
This change in case is similar to changes number and person and tense. All these are used in the Quran for rhetorical purposes in their contexts. This is a feature called iltifaat. Of which there are countless examples in Arabic. As for how these rhetorical measures are used in the Quran - they have been covered comprehensively in the largest book on Quranic sciences called Al-Burhan by Zarkashi.
The Second Error
"But those of them that are firmly rooted in knowledge, and the believers believing in what has been sent down to thee, and what was sent down before thee, that perform the prayer and pay the alms, and those who believe in God and the Last Day - them We shall surely give a mighty wage." (Arberry)
"Laakinir-Raasi-khuuna fil-'ilmi minhum wal-Mu'-minuuna yu'-minuuna bi-maaa 'unzila 'ilayka wa maaa 'unzila min-qablika wal-muqiimiin as-Salaata wal mu'-tuunaz-Zakaata wal-Mu'-mi-nuuna billaahi wal-Yawmil-'Aakhir: 'ulaaa 'ika sanu'-tii-him 'ajran 'aziimaa."
The word muqiimiin should be muqiimuun. The word should be declined by the "raf'a sign" like the other nouns in the sentence. Indeed the two nouns before it (Raasi-khuun and Mu'-minuun), and the noun after it (mu'-tuun) are declined correctly. Some have argued that this word was declined as such to distinguish and praise the act of praying, but the scholar Ibn al-Khatib says that this is a sick reasoning. (al-Furqan by Mohammad M. 'abd al-Latif Ibn al-Katib, Dar al-Kutub al-'elmiyah, Beirut, p.43). Such reasoning defies logic. Why would one distinguishe prayer which is a branch of religion, and not faith which is the fundamental and root of religion? Besides can this logic apply to the error of declension in the previous verse? Do we conclude that the Saabi'iin are more distinguished than those who believe, and the People of the Book? And why do they get distinguished in one verse and not the other as we have seen? God is much higher than this sick logic. This again is an obvious grammatical error.
This is the same feature which is covered by the answer to the first alleged error.
The Third Error
"They communed secretly saying, 'These two men are sorcerers'." (Arberry)
"Qaaluuu in haazaani la-saahiraani ..."
The word saahiraan should be saahirayn. The word saahiraan was declined incorrectly because the word in in the beginning of the nominal sentence causes a form of declension called "nasb" to the nominative and the "yeh" is the "sign of nasb". This is the third grammatical error.
This is another rhetorical feature and has been exhaustively dealt with by Arab linguists. For example T Hasan in his book Al-lugha Al-arabiyyah....
The Fourth Error
"It is not piety, that you turn your faces to the East and to the West. True piety is this: to believe in God, and the Last Day ... to give of one's substance ... and to ransom the slave, to perform the prayer, to pay the alms. And they who fulfil their covenant ... and endure with fortitude." (Arberry)
"Laysal-birra 'an-tuwalluu wujuuhakum qibalal-Mashriqi wal-Maghrib wa laakinnal-birra man 'aamana billaahi wal-Yawmil-'Akhiri wal-malaaa-'ikati wal-Kitaabi wan-nabiyyiin: wa 'aatal-maala 'alaa hubbihii zawilqurbaa wal-yataamaa wal-masaakiina wabnas-sabiili was-saaa-'iliina wa fir-riqaab: wa'aqaamas-Salaata wa 'aataz-Zakaata; wal-muufuuna bi'ahdihim 'izaa 'aahaduu was-Saabiriina fil-ba'-saaa'i wazzarraaa-'i ..."
In the above verse there are five gramatical errors. In four of them the wrong tense was used, as the sentence begins in the present tense with the verb tuwalluu, while the other four verbs were written in the past tense:
'aaman should be tu'minuu;
'aata shoud be tu'tuu;
'aqaama should be tuqimuu;
'aata shoud be tu'tuu.
The above verse when translated into English as it appears in Arabic would be: "It is not righteousness that ye turn your faces to the East and the West; but righteousness is he who believed in Allah and the Last day and the angels and the Book and the Prophets; and gave his wealth, ... and performed prayer and paid the alms." But the English translators have observed the tense, and the verbs "believed", "gave", "performed", and "paid" were corrected and written in the present tense. (For example see Arberry, Pickthall, Yusuf Ali and Rodwell's translations).
The fifth error is the wrong declension of the word saabiriina. It should be declined saabiruuna like the preceeding word muufuuna.
The first instance must be in present tense (like following the word to in English - "I am going to eat" not " I am going to will eat or "I have gone to ate". This is uncontentious as a rule of English grammar. Similar but different rules apply to Arabic grammar. If English were literally translated including the tenses into Arabic it would be gramatically completely incorrect. This alledged error is a basic misunderstanding of Arabic grammar. As for saabiuuna - see the response to the first alledged error.
The Fifth Error
"the likeness of Jesus, in God's sight, is as Adam's likeness; He created him of dust, then said He unto him, 'Be,' and he was." (Arberry)
"Inna massala 'Isaa 'indal-laahi ka-masali 'Adam; khalaqahuu min-turaabin-sum-ma qaala lahuu kun fa-yakuun."
The above verse when translated into English as it appears in Arabic would be: "The likeness of Jesus with Allah is as the likeness of Adam. He created him of dust, then He said to him 'Be,' and he is." The above is Pickthall's translation. Please note that he translated yakuun (is) as it appears in Arabic, i.e. in the present tense.
The word yakuun ("is" in English) should be kana ("was") to be consistent with the past tense of the previous verb "said" as it was corrected by Arberry, Rodwell and Yusuf Ali in their translations of that verse. This is the fifth error.
This a grammatical concept with an identifiable name in Arabic "Al-Hikaya" where you take a block and present it as it is without changing any part of it just as you dont change any part of an idiom to suit the different gender or number or tense. For example, when I presume to teach my school teacher some mathematics he may reply "dont teach your grandmother to suck eggs". He is not a grandmother and no eggs are being sucked. Is this a grammatical error on his part? No - you couldnt even change the idiom to "...suck an egg".
The Sixth Error
"The evildoers whisper one to another ..."
"Laahiyatan - quluubuhum. Wa 'asarrun-najwallaziin zalamuu..."
The word 'asarru should be 'asarra. The above is a verbal sentence, and the rule for such a sentence, where the verb comes before the (masculine) subject, is that the verb must be in the third (masculine) singular form, if the active subject of the verbal sentence is stated in the sentence. (The same rule holds for substituting the two mentionings of "masculine" by "feminine".) But the verb in the above Qur'anic verse came in the plural form. See how the above rule was observed in the following Qur'anic verses: 3:52, 10:2, 16:27, 16:35, 3:42, 49:14.
There are equally valid answers to this:
1, You can take "allaziin zalamuu" as in apposition to the plural pronoun to condemn them for their wickedness and declare that it was their wickedness that led them to the act.
2, This is a recognised acceptable dialectical variation in classical Arabic, known in all grammar texts as lughat akaluni al-baraghith where we have the plural pronoun (not singular) followed by the subject as in the verse above. Perfectly acceptable usage of classical Arabic.
The Seventh Error
"These are two disputants who have disputed concerning their Lord." (Arberry)
"haazaani Khismani 'ikhtasamuu fi rabbihim ..."
In Arabic, like English words are declined or conjugated with respect to number. In English there are two numbers: singular and plural. So in English two men are treated as plural. But in Arabic there are three numbers: singular, dual, and plural. So in Arabic the verbs and nouns are treated according to the singular or the dual or the plural. The verb in that verse was conjugated as if the subject is more than two. But the verse speaks only of two. So the rules of the dual should be followed and the word 'ikhtasamuu should be 'ikhtasamaa. So this is yet another error.
The dual refers to the two entities - the believers and the unbelievers and then the plural is refering to the plurality of the numerous individuals in each camp. In English we might say " It is german government who wants to ban British beef which they say they is dangerous." Government is both single and hence "it wants" and plural because the government has many people in it hence "they say".
The Eighth Error
"If two parties of believers fight, put things right between them." (Arberry)
"wa 'in-taaa-'ifataani mi-nal-Mu'-miniinaq-tatalu fa-'aslihuu baynahumaa."
This error in this verse is like the previous one. The number again is dual but the verb was conjugated as if the subject is plural. So the verb 'eq-tatalu should be 'eqtatalata.
This is exactly the same as the previous alleged error.
The Nineth Error
"O my Lord, if only Thou wouldst defer me unto a near term, so that I may make freewill offering, and so I may become one of the righteous." (Arberry)
"... Rabbi law laaa 'akhartaniii 'ilaaa 'ajalin-qariibin-fa-'assaddaqa wa 'akum-minas-salihiin."
The verb 'akun was incorrectly conjugated. It should be 'akuuna, i.e. the last consonant must have the vowel "a", instead of being vowelless, because the verb 'akun, is in the subjunctive. Indeed the previous verb ('assaddaqa) has been correctly conjugated and is in the subjunctive. The reason is that in Arabic the present tense is placed in the subjunctive mood if it is preeceeded by certain words (huruf nasebah). One of such words is the "causative fa".
Firstly there is a valid reading (one of the standard seven readings) in which this is "akuuna".
The explanation of this reading is that it is in conjunction with the mahall of 'assaddaqa which is jazm in the sense "if you delay me, I will give in charity and be of the righteous". atf ala al-mahall is a well known feature of Arabic grammar.
The Tenth Error
"By the heaven and that which built it." (Arberry)
"was-samaaa-'i wa maa ba-naahaa."
The word ma in the Arabic language is used for the impersonal. But the subject of the above verse is God. So the word which should be used is the Arabic word man (meaning "him who"). Arberry translated that verse as follows: "By the heaven and that which built it" meaning God. Pickthall however corrected the impersonal (ma, that which) and translated the verse as follows: "By the heaven and Him Who built it."
Indeed Pickthall also corrected the two verses that follow:
And the earth and Him Who spread it. Q. 91:6.
And a soul and Him Who perfected it. Q. 91:7.
Yusuf Ali, to get out of the problem, translated the above verse as follows: "By the firmament and its wonderful structure". So the subject 'God' does not appear at all in his translation of that verse. He gives his reason for his translation in a footnote saying: The ma masdariya in Arabic, in this and the subsequent clauses, is best translated in English by nouns." But the word bana in banaha is not a noun but a verb in the past tense as translated correctly by Arberry and Pickthall. The word ma should have been man (meaning "who") and in that context it should have been "Who" with a capital W.
"ma" in this verse is not a relative pronoun refering to God but "masdariyya" meaning "the building of it" not he who built it. Yusuf Ali having been brought up on the madrasa tradition knows better Arabic than either Arberry or Pickthal.
The Eleventh Error
"Then He lifted Himself to heaven when it was smoke, and said to it and to the earth, 'come willingly, or unwillingly!' They said, 'we come willingly.'"
"... faqal laha wa lel-Arad 'iteya taw'aan aw karha qalata atayna ta'e'een."
Heaven and earth in Arabic are feminine nouns, the verb said in "they said" is accordingly feminine and dual (qalata), but the adjective "willing" at the end of the verse is masculine and plural (ta'e'een), being at variance with the rule that the adjectives should match their nouns in number in gender, thus ta'e'een which is used for plural, should be ta'e'atain which is used for feminine dual.
There are several Heavens and serveral Earths. In classical Arabic they can be refered to as masculin or feminine. What you are talking about is a change that has occured in modern Arabic. You will be surprised for instance to know that in classical Arabic it is correct to say "qaala al-nisa and qaalat ar-rijal" both of which sound incorrect in modern Arabic. See also the response to the 7th alledged error.
The Twelfth Error
"The mercy of God is near."
"... inna rahmata Allahi qaribun min al-mohseneen."
The above verse is a nominal clause. In such a clause the predicate should match the subject (rahmata) of the nominal clause in gender. The word qaribun (meaning "near") is the predicate of rahmata Allahi ("mercy of Allah"), they should match each other in gender. But this is not the case in the Arabic text. Rahmata is feminine in Arabic and so the word qaribun (which is masculine) should instead be qaribah (its feminine form).
This rule was correctly observed in other Qur'anic verses. For example, in 9:40 we read: "Kalemat ul-llah heya al-'ulya." Here both Kalemat and heya are feminine. To say instead: "Kalemat ul-llah howa al-'a'la" would never be correct. That would be just as wrong as saying: "... inna rahmata Allahi qaribun min ..."
Such structure well known in classical Arabic and qaribun serves as an adverb rather than an adjective. This is another simplification of modern Arabic. Using modern Arabic grammar as your standard is like criticising Shakespeare because of his grammar differs from modern English!
"We divided them into twelve tribes."
"wa qata'nahom 'ethnata 'ashrata asbatan."
Instead of asbatan it should read sebtan.
In the Arabic it literally say "twelve tribes". That is correct in English but not correct in Arabic. In Arabic it should say twelve tribe because the noun that is counted by a number above ten should be singular. This rule is observed correctly for example in 7:142, 2:60, 5:12, 9:36, 12:4.
If Allah had said "twelve tribe" he would have kept it in the singular. But He is talking about the numerous asbat within each tribe. "asbatan" means grandsons not tribes and these within each tribe. For further reference go to Zamakhsharis tafsir. He mentions the objection and answers it.