An-Nisa' : 82

أَفَلاَ يَتَدَبَّرُونَ الْقُرْءَانَ وَلَوْ كَانَ مِنْ عِندِ غَيْرِ اللَّهِ لَوَجَدُواْ فِيهِ اخْتِلَـفاً كَثِيراً 

Do they not then consider the Qur'an carefully Had it been from other than Allah, they would surely, have found therein contradictions in abundance). (An-Nisa' : 82)

Allah commands them to contemplate about the Qur'an and forbids them from ignoring it, or ignoring its wise meanings and eloquent words. Allah states that there are no inconsistencies, contradictions, conflicting statements or discrepancies in the Qur'an, because it is a revelation from the Most-Wise, Worthy of all praise. Therefore, the Qur'an is the truth coming from the Truth, Allah.

This is why Allah said in another Ayah,

أَفَلاَ يَتَدَبَّرُونَ الْقُرْءَانَ أَمْ عَلَى قُلُوبٍ أَقْفَالُهَآ

 (Do they not then think deeply in the Qur'an, or are their hearts locked up (from understanding it))

Allah then said,

وَلَوْ كَانَ مِنْ عِندِ غَيْرِ اللَّهِ

(Had it been from other than Allah,)

meaning, had it been fraudulent and made up, as the ignorant idolators and hypocrites assert in their hearts,

لَوَجَدُواْ فِيهِ اخْتِلَـفاً

(they would surely, have found therein contradictions), discrepancies and inconsistencies,

كَثِيراً

(in abundance).

However, this Qur'an is free of shortcomings, and therefore, it is from Allah. 

Similarly, Allah describes those who are firmly grounded in knowledge,

ءَامَنَّا بِهِ كُلٌّ مِّنْ عِندِ رَبِّنَا

(We believe in it, all of it is from our Lord.) (Ali 'Imran : 7) 

meaning, the Muhkam sections (entirely clear) and the Mutashabih sections (not entirely clear) of the Qur'an are all true. So they understand the not entirely clear from the clear, and thus gain guidance. As for those in whose heart is the disease of hypocrisy, they understand the Muhkam from the Mutashabih; thus only gaining misguidance. Allah praised those who have knowledge and criticized the wicked.

Imam Ahmad recorded that `Amr bin Shu`ayb said that his father said that his grandfather said,

"I and my brother were present in a gathering, which is more precious to me than red camels. My brother and I came and found that some of the leaders of the Companions of the Messenger of Allah were sitting close to a door of his. We did not like the idea of being separate from them, so we sat near the room. They then mentioned an Ayah and began disputing until they raised their voices. The Messenger of Allah was so angry that when he went out his face was red. He threw sand on them and said to them,

«مَهْلًا يَا قَوْمِ، بِهَذَا أُهْلِكَتِ الْأُمَمُ مِنْ قَبْلِكُمْ، بِاخْتِلَافِهِمْ عَلى أَنْبِيَائِهِمْ، وَضَرْبِهِمِ الْكُتُبَ بَعْضَهَا بِبَعْضٍ، إِنَّ الْقُرْآنَ لَمْ يَنْزِلْ يُكَذِّبُ بَعْضُهُ بَعْضًا، إِنَّمَا يُصَدِّقُ بَعْضُهُ بَعْضًا، فَمَا عَرَفْتُمْ مِنْهُ فَاعْمَلُوا بِهِ، وَمَا جَهِلْتُمْ مِنْهُ فَرُدُّوهُ إِلى عَالِمِه»

(Behold, O people! This is how the nations before you were destroyed, because of their disputing with their Prophets and their contradicting parts of the Books with other parts. The Qur'an does not contradict itself. Rather, it testifies to the truth of itself. Therefore, whatever of it you have knowledge in, then implement it, and whatever you do not know of it, then refer it to those who have knowledge in it. )" 

Ahmad recorded that `Abdullah bin `Amr said,

"I went to the Messenger of Allah one day. When we were sitting, two men disputed about an Ayah, and their voices became loud. The Prophet said,

«إِنَّمَا هَلَكَتِ الْأُمَمُ قَبْلَكُمْ بِاخْتِلَافِهِمْ فِي الْكِتَاب»

(Verily, the nations before you were destroyed because of their disagreements over the Book.) 

Muslim and An-Nasa'i recorded this Hadith.