There are some who claim that the Quran is incomplete, that the Quran does not explain all things, and that certain issues and subjects must be consulted from other sources to get a clearer picture, such as going to the hadiths and tafsir. An example would be the prayers, to fully understand and learn how to pray one must consult the sunnah of the Prophet Muhammad (pbuh) which is to be found in the hadiths, hence the critics of the Quran argue that this proves the Quran is incomplete.

The critics also argue that the Quran is in contradiction as it claims to be a book that has explained things in detail:

006.114 
Say: “Shall I seek for judge other than Allah? – when He it is Who hath sent unto you the Book, explained in detail.” They know full well, to whom We have given the Book, that it hath been sent down from thy Lord in truth. Never be then of those who doubt.

010.024 
The likeness of the life of the present is as the rain which We send down from the skies: by its mingling arises the produce of the earth- which provides food for men and animals: (It grows) till the earth is clad with its golden ornaments and is decked out (in beauty): the people to whom it belongs think they have all powers of disposal over it: There reaches it Our command by night or by day, and We make it like a harvest clean-mown, as if it had not flourished only the day before! thus do We explain the Signs in detail for those who reflect.

030.028 He does propound to you a similitude from your own (experience): do ye have partners among those whom your right hands possess, to share as equals in the wealth We have bestowed on you? Do ye fear them as ye fear each other? Thus do we explain the Signs in detail to a people that understand.

So does the Quran get disproved when Muslims go to hadiths or tafsirs? Not really, because the Quran itself says:

004.080 
He who obeys the Messenger, obeys Allah: But if any turn away, We have not sent thee to watch over their (evil deeds).

So as you can see Muslims are commanded to obey the Prophet Muhammad (pbuh), and this verse explains the importance of obeying the prophet, that obeying the prophet is infact like obeying God since the prophet is conveying what God commanded. Hence when Muslims consult the hadiths and the sunnah of the prophet for explanations, this doesn’t disprove the Quran, rather it is following the Quran’s command. Because the Quran commands us to obey the prophet.

Here is another important verse:

2: 151- Similarly (to complete My Blessings on you) We have sent among you a Messenger (Muhammad SAW) of your own, reciting to you Our Verses (the Qur’ân) and sanctifying you, and teaching you the Book (the Qur’ân) and the Hikmah (i.e. Sunnah, Islâmic laws and Fiqh – jurisprudence), and teaching you that which you used not to know.

As you can see the Quran says that the Prophet Muhammad (pbuh) teaches people the book, so when people consult the hadiths where they find the Prophet Muhammad (pbuh) teaching us about the Quran, this doesn’t disprove the Quran as being incomplete, rather it is following the Quran.

The Quran is indeed complete, because it tells us that we should obey the prophet, and that the prophet teaches the book, so when we learn the book and learn certain things from another source such as the hadith it is following the Quran’s command.

Remember the previous quoted verse, which stated that obeying the prophet is like obeying God, hence when one takes knowledge and wisdom about the Quran from the prophet it is like taking it from God since the prophet got his wisdom and knowledge about the Quran from God.

So the Quran explains to us that we should infact go to the prophet to also understand the Quran and its rulings and teachings.

Had the Quran not instructed us to obey the prophet and consult him for explanations and rulings then one could say the Quran is incomplete, yet the Quran explains to us that we should consult the prophet who teaches the book so that we may understand it better, hence the Quran explains everything for us.

And here is another verse:

4: 59- O you who believe! Obey Allâh and obey the Messenger (Muhammad SAW), and those of you (Muslims) who are in authority. (And) if you differ in anything amongst yourselves, refer it to Allâh and His Messenger (SAW), if you believe in Allâh and in the Last Day. That is better and more suitable for final determination. 

The Quran commands us to obey those in authority, such as the scholars and the ones of knowledge, hence when we don’t understand something or need to have something explained to us then we should refer to these people in authority about the matter. The verse goes on to say that if we have any differences amongst ourselves then we should resolve this issue by first going to Allah, which means going to the Quran to see what Allah commands, and then secondly we should go to the prophet which means his sunnah which is to be found in the hadiths and see what it says. Hence in this verse the Quran is giving clear authority to the sunnah of the prophet which is to be found in the hadiths, only second to the Noble Quran.

So how can someone claim the Quran is incomplete when the Quran strictly commands us to refer to the prophet for guidance and instruction? How can someone claim the Quran is incomplete when it grants such a high authority for the prophet’s teachings and guidance?

This verse basically sums it all up, that Muslims have two sources to refer to for explanations, one which is the Quran which comes first, and the second is the sunnah of the Prophet Muhammad (pbuh), after this we can go to the ones in authority, the learned scholars and gather knowledge from them since the scholars are the inheritors of the prophets as the Prophet Muhammad (pbuh) taught.