Firstly: 

There is no difference of opinion among the scholars with regard to the interpretation of the entire Qur'aan. Rather they differed concerning the interpretation of some of its verses. There is no doubt that with regard to most of the verses, there is no difference of opinion as to their interpretation. Rather the commentators, both early and later, and scholars are agreed on its interpretation. This is something that is clear to everyone who reads the Qur'aan and books of commentary. The majority of Muslims still read the Qur'aan and listen to its verses, and most of them have no problem understanding most of it; rather they know what it means and this is sufficient to be guided by the Qur'aan. 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 

With regard to the saheeh reports which say that they differed concerning it and held conflicting views, these are very few compared to the verses concerning which they did not differ. End quote. 

Majmoo’ al-Fataawa, 5/162 

Secondly: 

Most of the differences that did occur came after the best (earliest) centuries. As for the Sahaabah and Taabi’een, the differences among them concerning the interpretation of the Qur'aan were very few. 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 

Hence the disagreements among the Sahaabah concerning the interpretation of the Qur'aan were very few. Even though there were more disagreements among the Taabi’een than among the Sahaabah, they are still few in comparison to what came after them. The more virtuous the era, the more consensus, harmony, knowledge and clarity about the Qur’aan there was. End quote. 

Majmoo’ al-Fataawa, 13/332. 

Thirdly: 

As for the few verses concerning the interpretation of which there was a difference of opinion (among the Salaf), they may be divided into several categories: 

(i)Those concerning which the difference has to do with variations of meanings, not conflicting opinions. So these are differences in wording, which do not affect anything and a difference in wording is not really a difference in fact, because if there is a difference the two opinions should contradict one another, and that is not the case in this category of differences.

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy upon him) said, commenting on differences in varieties of meaning: 

That is of two types:

The first type is where each of the commentators expressed what the words mean in wording different from that of his companions, which indicates that what is meant is a different shade of meaning, not a different meaning altogether, as they are referring to the same thing. This is like referring to a sayf (sword) as saarim or muhannad (other Arabic words for sword). The same is true of the beautiful names of Allah, the names of His Messenger (blessings and peace of Allah be upon him) and the names of the Qur'aan. The names of Allah all refer to the same One, and each of His names refer to the same Essence and the attribute reflected in the name. The same may be said of the names of the Prophet (blessings and peace of Allah be upon him), such as Muhammad, Ahmad, al-Maahi (the Eraser, by means of whom Allaah erases (yamhu) kufr), al-Haashir (the Gatherer, at whose feet the people will gather), and al-‘Aaqib (the successor, i.e., the one who succeeds the other Prophets in bringing about good, or the Last Prophet); and of the names of the Qur'aan, such as the Qur’aan, al-Furqaan (the Criterion), al-Huda wa’l-Shifa (guidance and healing), al-Bayaan (clarity), al-Kitaab (Book) and so on. 

Once this is established, one of the early generation sometimes referred to a thing with a word or phrase that referred to one of its attributes, and another would refer to it by a different word or phrase that reflected another of its attributes, like one who says: Ahmad [i.e., the Prophet (blessings and peace of Allah be upon him)] is al-Haashir, al-Maahi, al-‘Aaqib; and al-Quddoos (the Most Holy) is al-Ghafoor (The Oft Forgiving), al-Raheem (the Most Merciful). In other words, what is referred to is one and the same, but the attributes are not the same. It is known that this is not a contradiction as some people think. 

Another example of that is their interpretation of the phrase al-siraat al-mustaqeem (the straight path).  

Some of them said that it means the Qur'aan, i.e., following it. 

Some of them said that it means Islam. 

These two opinions are in harmony, because the religion of Islam is following the Qur'aan, but each one highlights a different shade of meaning that is not reflected in the other. 

The word siraat (path) may also indicate another meaning, as reflected in the view of those who say that it is al-Sunnah wa’l-Jamaa’ah (i.e., adhering to the Sunnah and the main body of the Muslims); and those who say that it is obedience to Allah and His Messenger (blessings and peace of Allah be upon him), and other examples, all of which indicate the same thing, but each looks at it from a different angle. 

The second type is where the Qur'aan uses a general word and each commentator mentions some specific type by way of example, in order to explain to the listeners the general meaning. 

That is like when a non-Arab asks what is meant by the word khubz (bread), and someone shows him a loaf of bread (ragheef) and says, “This”, although the word does not refer to this specific type or this particular loaf. 

Another example is what is narrated concerning the verse in which Allah says (interpretation of the meaning): “Then We gave the Book (the Qur’aan) as inheritance to such of Our slaves whom We chose (the followers of Muhammad صلى الله عليه وسلم). Then of them are some who wrong their ownselves, and of them are some who follow a middle course, and of them are some who are, by Allaah’s Leave, foremost in good deeds” [Faatir 35:32]. It is well known that the phrase “those who wrong their own selves” includes one who neglects the obligation of Islam and one who transgresses the sacred limits, and the phrase “those who follow a middle course” includes the one who fulfils the obligations of Islam and refrains from haraam things, and the phrase “those who are foremost in good deeds” includes the one who goes ahead and draws close to Allah by means of naafil good deeds in addition to obligatory duties. 

Moreover each of the commentators may mention different types of acts of worship (sc.) when commenting on this verse: 

One may say that the one who is foremost in doing good deeds is the one who prays at the beginning of the time for the prayer, the one who follows a middle course is the one who prays within the period for that prayer, and the one who wrongs himself is the one who delays praying ‘Asr until the sun has turned yellow [i.e., close to sunset]. 

Another commentator may say that the one who is foremost in doing good deeds and the one who follows a middle course and the one who wrongs himself are the ones who are mentioned at the end of Soorat al-Baqarah, where it describes the doer of good as the one who gives charity, the one who wrongs himself as someone who consumes riba, and the one who follows a middle path as being the one who is honest his dealings. 

Each interpretation refers to some qualities that come under the meaning mentioned in the verse so as to tell the listener that this is included in the meaning of the verse and to point to another shade of meaning. Explaining by giving examples is much easier than speaking in general terms, and the sound mind will understand that the example given refers to something more general, just as the one who is shown a loaf of bread and is told that this is called bread (khubz) understands that this word refers to bread in general and not just this particular loaf. End quote. 

Majmoo’ al-Fataawa, 13/332-338 

He also said (may Allah have mercy on him): 

It should be noted that the differences that arose among the commentators are of two types: 

The first type is those in which there is no contradiction, rather each view may be correct and it is no more than a variation in the shades of meaning or describing the same meaning from different perspectives. In most cases the differences that are proven to be from the commentators among the early generations, the Sahaabah and Taabi’een, are of this type. When Allah mentions something in the Qur'aan, such as the verse in which He says (interpretation of the meaning): “Guide us to the Straight Way (al-siraat al-mustaqeem)” [al-Faatihah 1:6], each of the commentators explained the straight path with a phrase which is indicative of some of its meaning or attributes, and all of that is true. So some of them said that the straight path means the Book of Allah or following the Book of Allah. Another said that the straight path means Islam, or the religion of Islam. Another said that the straight path means the Sunnah and the main body of the Muslims (al-Sunnah wa’l-Jamaa’ah). Another said that the straight path means the way of complete servitude to Allah (‘uboodiyyah) or the way of hope and fear, love of Allah, or obeying commands and heeding prohibitions, following the Qur'aan and Sunnah, striving to obey Allah and other words and phrases. 

It is known that what is referred to is one and that there are variations in attributes and wording.  

And there is another type, in which the commentator explained the meaning by giving an example without wanting to limit the meaning to the example he gave, such as when a foreigner says what does “bread” mean? And he is shown a piece of bread. End quote. 

Majmoo’ al-Fataawa, 13/381-384 

The second type is verses in which the differences concerning the interpretation are opposite or contradictory. This is very rare and applies to only a few verses; these differences are well known and limited. 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 

Differences concerning tafseer among the salaf are very rare; their differences concerning rulings are more common than their differences concerning tafseer. Most of the saheeh reports which speak of their differences have to do with variations on shades of meaning, not contradictory opinions. End quote. 

Majmoo’ al-Fataawa, 13/178 

There are many reasons for these differences and they have been studied by specialised scholars. The reader may consult Asbaab Ikhtilaaf al-Mufassireen by Prof. Dr. Muhammad al-Shaayi’ and Ikhtilaaf al-Mufassireen Asbaabuhu wa Athaaruhu by Prof. Dr. Sa’ood al-Funaysaan. 

Fourthly: 

This second type should not be a reason for doubting the validity of the Qur'aan for a number of reasons: 

1-It does not occur concerning any the verses that have to do with beliefs or the aims of Sharee’ah; rather it only occurs concerning the verses on rulings, such as the difference of opinion among the scholars on meaning of the verse (interpretation of the meaning): “And divorced women shall wait (as regards their marriage) for three menstrual periods” [al-Baqarah 2:228]: does al-qar’ (translated here as menstrual period) refer to purity or menses? Or it may occur in the commentary on some Qur’aanic contexts that have to do with stories or exhortation and the like, such as their difference of opinion on the meaning of the verse (interpretation of the meaning): “Then [the babe ‘Eesa (Jesus) or Jibreel (Gabriel)] cried unto her from below her, saying: “Grieve not: your Lord has provided a water stream under you” [Maryam 19:24]. -- is the one who called out Jibreel or ‘Eesa (peace be upon them both)? This difference of opinion -- as you can see -- does not have to do with the essence of belief or sharee’ah; rather it is a fiqhi matter in which Allah willed that some differences should occur out of mercy towards this ummah and also as a test; or it is a difference that does not affect the general meaning of the verse.

2-These differences -- although they are very rare -- mostly occurred among the later generations. If we go back to the tafseer of the early generations, the Sahaabah and Taabi’een, we would not find most of these differences that are found in later books of tafseer.

3-Finally, there is wisdom in the fact that the meaning of some verses is not quite clear, so that people will strive hard and there will be discussion of these verses and knowledge in books and people's minds.

Fifthly 

With regard to the claim that there is no contradiction in the Gospel or in the commentaries on the Gospel, this is very strange and weird. The Christians themselves make no such claim, because it is contrary to reality, as the copies, variations and translations of the Gospel differ a great deal and contradict one another. The Christians also have a lot of different branches and religious differences, and the differences in interpretation of the Gospel have to do with the foundations of their beliefs and the meaning of the Trinity, Divine Oneness and the three Persons (of the Trinity). This is a contradiction that led to the emergence of many branches which differ concerning the essence of faith and religion. But in the case of Islam and the Qur'aan, among the scholars of Islam of Ahl al-Sunnah (the Sunnis), who formed the majority of Muslims, from the time of the Sahaabah and Taabi’een until the present day, there are no differences concerning the basic foundations of the faith and its major teachings. 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 

The Christians' commentaries on their holy books contain distortions of the book of Allah and misinterpretation of the names of Allah and His Signs; it would take too long to describe them but you can never cease to be amazed by them. End quote. 

Al-Jawaab al-Saheeh, 3/93 

He also said: 

The Christians affirm that this phrase in the Gospel is taken from the Messiah but they differ as to the meaning of these words. Many of them say that the Father is existence and the Son is the Word and the Holy Spirit is life. Some of them say: Rather the Father is existence, the Son is the Word and the Holy Spirit is Power. And some of them say that the three Persons (of the Trinity) are: Generous, Wise and Able. So they say that the Father is generous, the Son is wise and the Holy Spirit is able. They claimed that all divine attributes are included in these three. I have seen all of that in the books of the Christians. And there are some who explain the Word as meaning knowledge, and some who say that it is self-sufficient, living and wise. They are all agreed that what is incarnated in Jesus is the incarnation of the word, and he is the one whom they call the Son, not the Father. Those who deny the incarnation, such as the Arians, say that Christ (peace be upon him) was a servant who was sent, like all the Messengers (blessings and peace of Allah be upon them). Although they agreed with them on using the terminology Father, Son and Holy Spirit, they did not interpret it as their opponents did as referring to incarnation. Similarly, the Nestorians also agreed with them on this terminology, but they differed with them concerning the incarnation in which the Jacobites and Melkites believe. 

And thus they agreed on the wording but differed on the meaning. It is known that they believed in this wording as part of their religion, because  they believe it is mentioned in their religion. But then they differed after that concerning the interpretation of the Book as they and all the followers of different religions differed concerning the interpretation of some words that they believed were transmitted from the Prophets (peace be upon them). End quote. 

Al-Jawaab al-Saheeh (3/189-192) 

And Allah knows best.