The similarities between the Qur'an and previous scriptures has been noted since the advent of Islam. However, the Judeo-Christian tales and their Qur'anic counterparts do not always match. There are three explanations for this:
- The original Judeo-Christian scriptures have been corrupted (as Muslims like to claim).
- Muhammad imperfectly borrowed from the Judeo-Christian scriptures.
- The Qur'an has been corrupted.
It is an epistemological matter as to which of the three is correct. The Qur'an’s assertion that the Judeo-Christian scriptures have been corrupted is mere accusation devoid of evidence. To prove corruption of an older scripture, it is logically necessary to provide tangible evidence such as an extant copy of an uncorrupted manuscript. However, to prove a later scripture has either been corrupted or is an imperfect derivation of the previous scripture, one merely has to compare the texts – if one is unable to prove the older scripture has been corrupted then it stands to reason the latter two explanations are likely.
Note: I take the word ‘corruption’ in this context to mean a substantive alteration of the textual meaning, not the change of words or other translational changes.
No Muslim has ever been able to provide irrefutable tangible evidence that the Judeo-Christian scriptures have been corrupted. Even the Dead Sea Scrolls dating back to at least the Third Century BC can be of no help to the Muslim proposition. So all we have from Muslims is the Qur'an, and what it has to say on the subject is irrelevant if Allah did not see fit to prove himself with tangible evidence.
On the other hand, it is easy to point out the imperfect ‘borrowing’ from previous scripture in the Qur'an. Muslims speculate that these are merely due to Allah ‘correcting’ the corruption which had crept into the previous scriptures. Prima facie - this is a good argument, as is the 'similarity due to a single source' argument. It would be interesting to take a closer look at the relevant texts and their purported sources of origin.
It is a common proposition that Muhammad most likely borrowed from previous scripture from hearing scriptural accounts told by Christians and Jews. As he was an unscholarly man, it is unlikely that he read any previous scriptures, hence the imperfection of his borrowing. I believe that it is not commonly asserted that these previous scriptures from which Muhammad ‘borrowed’ the Judeo-Christian tales were translated into Arabic in his day as the Quran and hadiths suggest Jews and Christians were present to do the translation into Arabic for all and sundry to hear.
Old Charges of Borrowing
Many contemporaries of Muhammad commented on the similarities between the Qur'an and previous scripture: the Meccans pagans already knew the tales from previous scriptures (i.e. Judeo-Christian tales) – they called Muhammad’s version of them the “tales of the ancients”. Muhammad griped against this oft-leveled charge. It must have irked him so much that it warranted eight verses, composed over a number of years.
These verses are all found in the Meccan Qur'an, despite the fact that some of these verses have been inserted into Medinan suras, such as Sura al-Anfal 8. Scholars are unanimously agreed on the fact that these aforementioned verses are indeed Meccan, despite the suras in which they are now found. What one can gather from this is that the unbelievers, who spoke of the fairy-tales of the ancients in the Qur'an, were of the people of Mecca. None adopted this opinion in Medina after the migration.
A check of Maududi’s commentary confirms this. Maududi: Surah 6 - last year of the Holy Prophet's life at Makkah; Surah 8 - in 2 A. H. after the Battle of Badr; Surahs 23 & 27 - the middle stage of Prophethood at Makkah; Surah 25 - during the third stage of Prophethood at Makkah; Surah 46 - towards the end of the 10th year or in the early part of the 11th year of the Prophethood; Surah 68 - one of the earliest surahs to be revealed at Makkah; Surah 83 - in the earliest stage at Makkah.
One verse has the Meccan pagans accusing Muhammad of “making ancient tales written” (i.e. iktatabaha) that were recited (i.e. dictated) to him Quran 25:5. Thus, the Qur'an itself alludes to the charge of ‘borrowing’ of Biblical tales against Muhammad even in the earliest days of Islam.
(Translations from Qaribullah & Darwish)
The evidence that at least some of these tales of the ancients were Judeo-Christian tales and not that of the fanciful Quranic “Arabic/Arabized” fairy-tales of Jinns, Houris and the like is the context, particularly those relating to the Resurrection, and the charge that another nation had supplied these tales (meaning the Jews and possibly also Sabeans and Christians).
There is a sahih hadith that shows, without doubt, that the Arabs had heard the Judeo-Christian tales from the Jews. The implication of the hadith is that these tales were common-place from the phrase, ‘used to explain…’, so much so as to warrant Muhammad’s warning to the Muslims to both disbelieve and believe the Jews.
The following sahih hadith strongly suggests Muhammad was susceptible to ‘absorbing’ Jewish tales:
Note how Aisha noticed Muhammad vigorously adopting the Jewish belief of ‘punishment in the grave’ only after she had told him the tale. Before she told him she never saw this belief in him.
Possible Sources from the Ancient Tales
Who did Muhammad learn the Judeo-Christian tales from? There is strong evidence from the sahih hadiths that he learned at least some of them from Zaid bin 'Amr bin Nufail. These hadiths show that Zaid told the then still-pagan Muhammad about Allah and the religion of Abraham. Also note how Zaid claimed before the Ka'aba that he was the only one of the Quraysh who followed the religion of Abraham which he learned from a Jew and a Christian.
Narrated Ibn 'Umar: Zaid bin 'Amr bin Nufail went to Sham, inquiring about a true religion to follow. He met a Jewish religious scholar and asked him about their religion. He said, "I intend to embrace your religion, so tell me some thing about it." The Jew said, "You will not embrace our religion unless you receive your share of Allah's Anger." Zaid said, "'I do not run except from Allah's Anger, and I will never bear a bit of it if I have the power to avoid it. Can you tell me of some other religion?" He said, "I do not know any other religion except the Hanif." Zaid enquired, "What is Hanif?" He said, "Hanif is the religion of (the prophet) Abraham who was neither a Jew nor a Christian, and he used to worship None but Allah (Alone)" Then Zaid went out and met a Christian religious scholar and told him the same as before. The Christian said, "You will not embrace our religion unless you get a share of Allah's Curse." Zaid replied, "I do not run except from Allah's Curse, and I will never bear any of Allah's Curse and His Anger if I have the power to avoid them. Will you tell me of some other religion?" He replied, "I do not know any other religion except Hanif." Zaid enquired, "What is Hanif?" He replied, Hanif is the religion of (the prophet) Abraham who was neither a Jew nor a Christian and he used to worship None but Allah (Alone)" When Zaid heard their Statement about (the religion of) Abraham, he left that place, and when he came out, he raised both his hands and said, "O Allah! I make You my Witness that I am on the religion of Abraham."Narrated Asma bint Abi Bakr: I saw Zaid bin Amr bin Nufail standing with his back against the Ka'ba and saying, "O people of Quraish! By Allah, none amongst you is on (sic: of ?) the religion of Abraham except me." He used to preserve the lives of little girls: If somebody wanted to kill his daughter he would say to him, "Do not kill her for I will feed her on your behalf." So he would take her, and when she grew up nicely, he would say to her father, "Now if you want her, I will give her to you, and if you wish, I will feed her on your behalf."
Even the prohibition of female infanticide was inspired by Zaid. How often did Muhammad hear these stories from Zaid? The hadiths do not tell. However, one notes that the sira recounts Zaid’s withdrawal from Meccan society (where he was allegedly persecuted) to a cave in Mount Hira. Muhammad apparently visited the same cave at Ramadan on a yearly basis, an act his wife Khadijah said was the custom of his tribe as an act of penance.
Thus, it can be seen that there was ample opportunity for Muhammad to learn from Zaid long before the first revelation in 610 AD. Some say Muhammad first went to Mt Hira when he was around 35, i.e. around 605 AD. It is possible that Muhammad first visited Mt Hira when he was 33, when the “first unseen secrets” revealed themselves to him. Zaid died around 607 AD. The cave in Mt Hira is very small, measuring 4 yards long and 1.75 yard wide – there seems no way Zaid and Muhammad could have avoided each other. Clearly they knew each other; the sahih hadiths make that apparent, and we also know that Muhammad spent weeks and months in that cave which Zaid was reputed to have lived.
Zaid’s religious principles were also adopted by Muhammad
- the prohibition of killing infant daughters by burying them alive, according to the cruel custom of the Arabs of the time.
- the acknowledgment of the Unity of God.
- the rejection of idolatry and the worship of Al-Lat, AI-'Uzza' and the other deities of the people.
- the promise of future happiness in Paradise or the "Garden".
- the warning of the punishment reserved in hell for the wicked.
- the denunciation of God's wrath upon the "Unbelievers".
- And also, the application of the titles Ar Rahman (the Merciful), Ar Rabb (the Lord), and Al Ghafur (the Forgiving) to God.
Moreover, Zaid and all the other reformers (Hanifs) claimed to be searching for the "Religion of Abraham." Besides all this, the Qur'an repeatedly, though indirectly, speaks of Abraham as a Hanif, the chosen title of Zaid and his friends.
Argumenta ad hominem-loving Muslims who malign answering-islam for the above, should note that it references Ibn Ishaq’s Siratu’Rasul. The main thrust of Zaid’s story in the sira conforms to the reported meeting with Muhammad, and Zaid’s anti-female infanticide stance, in the sahih Bukhari hadiths.
Even the Muslim method of prayer may have originated from Zaid, as Ibn Ishaq (pg. 99-100) wrote that he prayed by prostration on the palm of his hands.
Another possible source of Judeo-Christian stories is Umm Habiba bint Abu Sufyan, Muhammad’s eighth wife. Her former husband Ubaydullah b. Jahsh was a Christian who converted to Islam and migrated with other Muslims to Abyssinia, there to reconvert to Christianity. However, this is admittedly mere conjecture. Other critics name Mariah the Copt but the evidence is against her being the source of Muhammad’s Judeo-Christian borrowings as she was presented to Muhammad when he was residing in Medinah, long after he included the Judeo-Christian tales in his ‘revelations’.
There is yet another hint in the Qur'an that Muhammad was influenced by a ‘foreigner’.
Who is this non-Arab who taught Muhammad? Could it have been Salman the Persian (who was a Christian) or Bahira the disgraced Nestorian?
The evidence for Salman is not strong and some say it was Bahira.
Islamic sources report that Muhammad, already at the age of nine to twelve, made his first journey with a trade caravan to Syria where he came in contact with Christians. We also know that on a second visit to Syria he showed great interest in the Judaism and Christianity he encountered there. He spent some time during that period with a Nestorian Christian monk named Bahirah. 
However the evidence is not convincing that it is Bahira that told Muhammad the Judeo-Christian stories.
Perhaps the strongest evidence of the ‘foreigner’s’ identity comes from the Sira:
This source specifically names the foreigner to be Jabr, slave of B. al-Hadrami.
Then there is this sahih hadith that specifically informs us that Muhammad learned from a Christian:
This Christian who taught Muhammad is not named in the sahih hadiths. However, Ibn Warraq, citing Waqidi, names him as ibn Qumta.
Waqidi [d. 207 AH D/823 CE] who says that a Christian slave named Ibn Qumta was the amanuensis of the prophet, along with a certain ‘Abdallah b. Sa‘ad b. Abi Sarh, who reported that "It was only a Christian slave who was teaching him [Mohammed]; I used to write to him and change whatever I wanted."
Regardless who this foreigner who taught Muhammad was, it is clear that this highly specific charge was leveled against Muhammad, and he revealed the aforementioned verse to ‘deflect’ it. That this foreigner existed is real: the Qur'an itself alluded to him by saying, ‘the tongue of him at whom they hint is a non-Arab’. Why would Muhammad say this? He admits there was someone (who taught him) whose tongue was not Arabic.
That this foreigner taught Muhammad the Judeo-Christian tales is alluded to when one follows Muhammad’s apologetic against this complaint in Surah 16. What follows Quran 16:103 is Muhammad talking how Allah revealed the religion of Abraham, the Resurrection, the Everlasting Life, Judgment Day, prohibition of meat of swine and non-halal slaughter, and other practices given to the Jews.
In short, verse Quran 16:103-104 is nothing more than Muhammad's attempt to answer the charge that he learned the Jewish/Christian religion from a foreigner (probably Jabr). He was the Muslim who first came up with the excuse that the similarities between the Judeo-Christian religion and the Qur'an are due to the three scriptures sharing the same source, which he named as Allah.
Thus it is evident that Muhammad heard Judeo-Christian tales from various sources, beginning with Zaid bin 'Amr bin Nufail and from Waraqa bin Naufal bin Asad bin 'Abdul 'Uzza, to Jabr and the un-named Christian of Sahih Bukhari 4:56:814
In the literature, Muslims commit red-herrings and straw-man arguments to deflect attention from the fact that their own sources, i.e. the Qur'an, hadiths and sira, confirm that Muhammad had borrowed ‘tales of the ancients’. The Muslim responses are as follows:
1. There were no Arabic copies of the Judeo-Christian scriptures available to Muhammad.
This is a straw-man argument as the Quran itself claims the charges were that Muhammad heard what was recited to him Quran 25:4-6 or that he learned them from a foreigner Quran 16:103-104. Thus, the existence or otherwise of Arabic translations in Muhammad’s time is an irrelevancy.
2. There was no center of Judaism and/or Christianity in Mecca or the Hijaz in Muhammad’s time.
This is another straw-man argument. As the Islamic literature itself shows Muhammad learnt the ‘tales of the ancients’ from individual Jews and Christians, some of whom we know by name, there is no need for Muhammad to learn from centers of Judaism or Christianity. Whether or not there were any Christian proselytizing in Mecca, is irrelevant: all it takes is one Christian individual (as in Sahih Bukhari 4:56:814) for Muhammad to learn from.
3. There is no evidence that Muhammad borrowed these tales even though there were Jews and Christians in the region.
The evidence is clear for all to see. The charges of borrowing are in the Qur'an. The evidence of borrowing is in the hadiths and sira: the individuals who taught Muhammad the Judeo-Christian tales were named.
4. The Jews were in Medinah and the Christians were in Najran and Yemen.
This is a red-herring and a clear error. Jews and Christians were certainly present in Mecca, for instance Jabr the Christian slave. Waraqa, Khadijah’s cousin also lived in Mecca, and so did the Hanif Zaid bin ‘Amr. We also know from Ibn Sa'd, that contact with Christian people was not unusual:
It is even possible that the Ka’ba contained a biblical quote:
It is often said by Muslims that there were no Jews in Mecca but only in Yathrib and surrounding areas of Northern Hijaz. This is untrue. It is possible that the Ka’aba contained pictures of Abraham and Mary. While not evidence of Jewish presence, it is certainly strongly suggestive of it.
The sira of Ibn Ishaq provides evidence that, while there was no major Jewish community, there were certainly Jews present in Mecca. It is said that when the Quraysh rebuilt the Ka’aba they found a Syriac inscription they were unable to read; a Jew read it for them. 
5. The Qur'an contains stories absent in the Judeo-Christian scriptures, thus the charge of borrowing is erroneous.
This is another straw-man argument. Nobody claims Muhammad copied the Judeo-Christians texts exactly nor limited his scope to these prior texts.
- Ignorance and illiteracy - A Struggle that Led to Conversion
- Siratu' Rasul, vol. i, p. 79.
- Abul Kasem - Who Authored the Qur’an?—an Enquiry mukto-mona
- Hughes' Dictionary of Islam, p. 30, quoting Tafsir-i-Husaini, Sale p. 223 and Muir's Life of Mahomet, p. 72
- The Holy Qur`ân, Ali, p.7, note
- Muhammad the borrower – Debate 2 with Saifullah
- Summary by Sharon Morad, Leeds - The Origins of The Koran: Classic Essays on Islam's Holy Book, edited by Ibn Warraq (Prometheus Books: Amherst, New York. 1998)
- Muhammad the borrower – Debate 2 with Saifullah
- Sirat Rasoul Allah - Introduction - faithfreedom.org