There are basically four different sources for the mistakes in the Qur’an. Let us consider these four sources as listed below:

Mistakes Muhammad was not responsible for but can be attributed to the environment he lived in.
Mistakes of Muhammad that came from his limited Bedouin perspective.
Mistakes of Muhammad that he knowingly committed and developed.
Mistakes in the Qur’an intentionally committed by translation.

1. First, let us consider mistakes that do not come from Muhammad himself but from the environment in which he lived.

a) The first mistake is from the Jews. Muhammad tried to win the Jews to Islam and convert them into Muslims. Therefore, he adapted all of what the Jews had said to him about Abraham, Moses, David and so on. He wrote it down to look as if he were a Jew. Muhammad contextualized Islam to the extent that it looked as if it were a Jewish religion. However, the mistake was that the Jews did not tell Muhammad the real text from the Old Testament, but the Old Testament in the form of stories from the Mishna and the Talmud. Therefore, what he wrote down was incorrect; not a single sentence of what he had heard was the real truth. The Mishna and Talmud have fantastic stories about Moses and other things that are absolutely not biblical. E.g. the story that Satan came about because he was cursed for not falling prostrate to Adam when God asked him. This is not from Muhammad but from the Talmud. It is an explanatory story; it is not revelation. As in many stories like these, the mistakes did not come from Muhammad. He learned about them from Talmudic and Mishna stories. Therefore, Muhammad is not to blame for these mistakes. Approximately 60% of the Qur’an is made up from such orally transmitted stories about the Old Testament. A comparison of these Old Testament stories in the Qur’an with the revealed text of the Old Testament exposes the mistakes he received from the Jews. Why did the Jews deceive him? Maybe some Jews played with Muhammad. Maybe they did not know the stories very well. They wanted to make money and Muhammad was like a dry sponge. He wanted to know it. They laughed at him and told him stories, unbelievable stories.

b) Muhammad also received folklore stories from the Christians that were not true. In the Syrian area, the Syrian Christians had fantastic stories about the childhood of Jesus. Fake Gospels, fake books and fake stories had been circulated. E.g. Jesus, as a child, spoke immediately after birth in the manger. When Muhammad heard this, he believed it. He believed more than we believe about Jesus, because he believed these fables. He could not distinguish between the truth and fables. Christians did not exactly tell him the truth. Muhammad used children’s stories that mothers told to quiet their children and put them to sleep. E.g. As a boy, Jesus took clay, formed it into a bird, blew in it and then the bird came to life and it flew away (Sura 5:110). We know, today, in which books this had been written before Muhammad lived. Of the Syrian Christians, there are four or five books in which these stories are written. Muhammad heard it and believed it. He had been deceived by superficial or Sufi minded Christians.

Muhammad also met Copts and they had very different views. They made Jesus a God, writing that Jesus is God himself. Jesus, because he was God, did not become God in body, but only appeared as a man, yet he was not a man. The Copts believed it impossible for God to use a toilette. They alleged that when Jesus appeared as a man, he was really not a man; he was really God. They believed that God could not die, thinking if God were to die the whole universe would explode. Therefore, they believed he only appeared to have been crucified but he was not crucified. Muhammad also adopted this view that Jesus was not crucified but it only appeared to them to be so (Sura 4:157). Muhammad took stories from the Syrian Christians, who spoke about the life of Jesus as a child, and bad theology from the Copts, who made Jesus a God and not a man. There was no balance regarding the being of Jesus in the Middle East; man could only be man and God could only be God.

Muhammad was not at fault for such stories. He heard them, and he incorporated them into his system. His source was incorrect.

In the Middle East, there were many Christians who honored Mary. They nearly made Mary a Goddess. They considered Mary the greatest of all women. A Christian sect even said that the Trinity is composed of Father, mother and Son, (i.e. God, Mary and Jesus.) No Christian church today believes such things. Because Muhammad wanted to please the Christians in order to convince the Christians to become Muslims, he dialogued with them about theological issues. In the process, Muhammad came to believe the Christian Triune God was three gods made up of Father, mother and Son. Muhammad's so-called revelation (Sura 5:116), in which he rejects this false trinity, reflects his personal unawareness due to false information acquired from a Christian sect.

Muhammad tried his best to appear to the Jews as a Jew, to the Christians as a Christian and to the Animists as an Animist in order to make Muslims of them all. Consequently he adopted such things from the Jews, the Christians and from various different sects. He included all of these mistakes in the Qur’an as revelation of Allah and now Muslims claim these sectarian thoughts as the revealed truth of God. The source of these mistakes is not Muhammad; it is those who taught him these things.

c) Enmity between the Jews and Christians was another source of confusion in Muhammad's search to know God. The Christians fought the Jews because the Jews said, “Christ is not the Messiah,” and “Christ is not the Son of God.” The Jews fought the Christians because the Christians said, “You don’t know who God really is” and “You do not know the Spirit of God, you are only in the old covenant and do not know the new covenant of God.” They quarreled in front of Muhammad. It is written in the Qur’an, “The Jews say, the Christians are nothings and the Christians say, the Jews are nothings” (Sura 2:113). Out of this enmity, all of what one said against the other was incorporated into the Qur’an. Muhammad said: “God will punish you at the day of judgement for the differences you have among you.” He really wanted to know the truth and what he found were differences between Jews and Christians, as well as differences between right-wing Christians and left-wing Christians. He was very puzzled. Therefore, he accepted what he heard. He thought about these things and incorporated them into his own beliefs. In essence, he formed his own dough with ingredients from other religions and baked his own bread.

We have considered the first source of mistakes. They did not come from Muhammad himself but from Jews and Christians in his surrounding. Let us be merciful with Muhammad regarding these errors. We must be honest and consider the truth of how these errors came to being.

2. Other mistakes from Muhammad, which may not be his personal fault, can be attributed to his way of thinking as a Bedouin who had settled down after doing much trading by way of traveling caravans.

If you have ever lived with Bedouins in their tents and have slept with them, you know how they talk and sing around the fire in the evening. They have fantastic memories and fantastic fantasies. They have dreams, they have visions, but they actually have a very limited horizon. They have not studied history; they have no schools with geography, mathematics or physics. Most of them have no education at all. They only have their flocks of sheep with a huge sky over them at night and a blazing sun over them during the day. They typically believe in animism. Although they do not lack wisdom, they are part of a limited culture with a limited horizon. Because Muhammad lived among this culture, you find in the Qur’an that he mixed up names and people he had heard about. See the following examples listed below:

Muhammad declares Haman to be the advisor of Pharaoh, but Haman was in Babylon in the Jewish history. In the Qur’an he appears as the advisor of Pharaoh not the advisor of the king in Babylon.
He announces the Samaritans as the creators of the Golden Calf. He confused the Samaritan tribe that came nearly 700 years after Aaron with the twelve tribes of Israel in the desert.
He reports Mary, the mother of Jesus, be the sister of Aaron, because both have the same Arabic name, Mariam. So Miriam, the prophetess and sister of Moses and Aaron is also the mother of Jesus in the Qur’an. This is because the Arabic language has no (plusquamperfect in Latin) perfect in the perfect tense. What is finished is finished; what is going on will go on forever. So the limited horizon of the culture caused him to overlook the importance of 1,300 years between these two different individuals. So Mariam the sister of Moses became Mariam the mother of Jesus. Miriam and Mary in the Bible became one Mariam in the Qur’an. This is because of the non-historical aspect of Islam.
He has Jesus being born in the desert, not in Bethlehem. Since he was a Bedouin, he imagined Mary sitting at the trunk of a palm tree when it came time to give birth.

We should also understand that Muhammad did not have the Holy Spirit in him. Therefore, he could not understand spiritual things. He had to explain them in a biological sense. It was not within his capability to grasp or understand them. He had a limited horizon. Understanding that fact will better help you understand what is written in the Qur’an.

Muhammad adopted laws of the Quraish tribe into Islam. In Mecca, there was polygamy, the right of a husband to strike his wife and laws of inheritance prior to the revelations given to Muhammad. He did not make new laws; he simply confirmed the existing laws. He incorporated his Bedouin logic and his Bedouin culture into the Qur’an.
All the stories about paradise and hell are visions of a vivid imagination. Like a Bedouin traveling in the desert who dreams of water, green plants, fruits and various pleasures, Muhammad made paradise a fabulous garden with trees, plants and pleasures – all fulfilling mans earthly human senses. This is the Bedouin horizon or Bedouin logic. Consequently, hell is fire. The midday desert sun can make you think your head is going to explode like a pressure cooker. So, Muhammad made pictures of hell similar to what he was familiar with, very much like the stories he heard. This is the culture of the Bedouins.
Muhammad also incorporated Jihad, the Holy War philosophy, into Islam. Revenge is a commitment. If a Muslim were to forgive, this would be a sin because he has no right to forgive. He must take revenge. On the other hand, Christians can forgive because Jesus has forgiven. Jesus has forgiven not only our sins but also the sins of others. We are commanded to forgive. A Bedouin is compelled to not forgive. If he would forgive, it would be a crime because sin has to be punished. It is an issue of pride. They do not have the privilege to forgive. Muhammad was a Bedouin and this is best understood from that prospective.

Thus far we have discussed two different kinds of mistakes in the Qur’an. The first were the mistakes Muhammad had learned from Jews and Christians and the stories they did not clearly or accurately tell. The second were mistakes or shortcomings that came from the environment or culture of the Bedouins. Now let us consider the third source.

3. Mistakes he created purposely. These are serious mistakes.

When he had either heard wrongly or written wrongly, the Jews and the Christians sometimes told him, “Muhammad this is wrong.” He said, “No, this is not wrong, but you are wrong and I am right.” When they said to him, “In the Torah, it is written precisely this way, you should correct your Qur’an,” he said, “No, the text in your Bible was originally revealed true and faithful, but what you have in your hand, must have been altered, it must have been changed, because I have the true revelation.” So, he did not agree to be corrected. If he would have admitted that he was mistaken, he could no longer be called a prophet. For the sake of his prophethood, he attacked the others and confirmed the mistakes as truths. They reasoned with him saying, “These are mistakes.” The Jews and Christians tried to correct him, but he attacked them saying, “No, never. I am right and you are wrong. Therefore, your book was revealed without mistakes, but what you have in your hand must have been altered.” He did not accept corrections. Therefore, Muhammad became an anti-Christian, hardening his heart against the truth. Had he accepted correction, this would have proven that he was not a prophet because he could not distinguish between the truth and fables. If you look closely at these mistakes you will find this is a serious problem with the Qur’an.

4. There is a fourth kind of purposely-introduced mistake. These are introduced by the translations. (To a Muslim, the Qur'an in any other language other than Arabic is not a Qur'an, it is merely an interpretation of the Qur'an.)

Of all the known English translations of the Qur’an, there is not one that is true to the text. Consider The Glorious Qur’an translated by Pickthall—what nonsense! No Muslim says that the Qur’an is glorious. It is said, the Qur’an is either (karim) "noble" or it may be referred to as the wise Qur’an, but no Muslim says the glorious Qur’an in Arabic. So Pickthall made the noble or wise Qur’an glorious. In fact he made everything in the Qur’an more glorious than it is written in Arabic. If there is a strong point that is somewhat offensive, Pickthall makes it glorious. He purposely polished up the Qur’an in his translation.

Another example is a translation by anti-Christian, Yusuf Ali. All texts concerning Christ have been made to appear a little bit weaker to the reader. Ali purposely introduced mistakes into his translation of the Qur’an.

There is no possibility to have a real comprehension of the text of the Qur’an unless you learn Arabic. You will never succeed in learning the Qur’an by being clever – you must be stubborn. You must stubbornly learn three to four vocabulary words every day. The problem with the Qur’an is not the grammar, the problem is the endless vocabulary it uses. The Arabic grammar is like the Hebrew grammar. If you have studied Hebrew as theologians do, there is similar grammar in the Qur’an – the same system, the same problems, and the same possibilities. Some people are gifted in languages, but they cannot learn the Arabic of the Qur'an by this gift; you must learn it by heart. If you don’t learn the vocabulary of the Qur’an by heart, you will never grasp it. If you learn the 1,000 most important words of the Qur’an, you will be able to study the whole Qur’an. Other words can be looked up in a dictionary. Arabic is not a difficult language. However, it has an endless number of words that you must memorize. Therefore, if you want to learn the Qur’an, you need to learn the Arabic vocabulary.

We have seen that the Qur’an has many mistakes from many different sources. Now let us consider the kind of mistakes found in the Qur'an.

There are at least 12 geographical mistakes in the Qur’an. Muhammad did not use many geographical statements, probably because he was not well versed in geography. He did not say, “It was in this region" or "that region," or "it was in this town" or "that town.” He said things like, “Eastward" or "in the desert,” in order that no one would catch him in an error. He did not make many references to geography because he was unsure. But in 12 places where he used such terms, he was definitely mistaken.
Muhammad has 55 historical mistakes in which he clearly put people, places and stories in the wrong place and at the wrong time.
He has 9 contradictions relating to the conscience of people wherein people murder other individuals and he declares it halaal, or allowed.
He has 29 theological differences, where what he said about God, the Christ and the Holy Spirit is definitely wrong.
He has at least 25 grammatical mistakes in the Arabic language. He used the accusative case for the genitive case and the genitive case for the accusative case and so on. Any Arabic scholar or Arabic student can tell you these are mistakes. Again, you must know Arabic in order to recognize them. The Qur’an is not infallible. The Qur’an has Arabic grammar mistakes.
There are 21 sociologic mistakes.
There are 22 scientific mistakes.
There are 30 uses of plagiarism, where he used terminology and phrases from other books and religions and used them as though they were his revelation.
There are 65 mistakes or contradictions in the life of Muhammad himself. Some he confessed as mistakes, others he did not.

Unfortunately, exhibiting and explaining the detailed mistakes in the Qur'an is beyond the scope of this article. This is designed to explain the sources of mistakes in the Qur'an and to provide a short overview of the kinds of mistakes in the Qur'an.