Knowledge of Arabic is not sufficient for understanding the Qur’aan:
From what has been stated previously, it becomes clear that there is no way for anyone, even if he be a scholar of the Arabic Language and its disciplines, to understand the noble Qur’aan, without seeking assistance in that from the Prophet’s Sunnah in speech and action. This is since he will never be more knowledgeable of the language than the Companions of the Prophet, those who the Qur’aan was revealed to in their language. And (at that time) the language was not blemished with the errors of the non-Arabs and the slang of the common people, but in spite of that, they still erred in understanding these previously mentioned ayaat, when they relied on their knowledge of the language only.
So based on this, it is obvious that whenever a person is knowledgeable of the Sunnah, he will be more likely to understand the Qur’aan and extract rulings from it, than someone who is ignorant about it. So how about the one who doesn’t rely on it or reference it at all? This is why from the principles that have been agreed upon by the people of knowledge is: to interpret the Qur’aan with the Qur’aan and the Sunnah,1 and then the sayings of the Companions, etc.
From this, we become aware of the misguidance of the scholars of rhetoric, past and present, and their opposition to the Salaf, in their Creed, not to mention their rulings. And it is their remoteness from the Sunnah and their knowledge of it, and their making their intellects and desires as judges for themselves with regard to the verses concerning Allaah’s Attributes. What is better than what has been stated in Sharh Al- ‘Aqeedah At-Tahaawiyyah [of Ibn Abil-‘Izz Al-Hanafee] (pg. 212, 4th Edition):
“How can someone who didn’t learn from the Book and the Sunnah, but rather just learned it from the views of so and so, speak about the fundaments of the Religion! And if he claims that he is taking it from the Book of Allaah, then he is not taking the interpretation of the Book of Allaah from the ahaadeeth of the Messenger. He doesn’t look into it (i.e. the Sunnah), nor does he look at what the Companions or those who succeeded them in goodness said, which has been conveyed to us by way of reliable narrators chosen by the critics (i.e. hadeeth scholars). For indeed, they did not convey the arrangement of the Qur’aan only, but rather they conveyed the arrangement as well as the meanings. They would not learn the Qur’aan like the children do (today), rather they would learn it along with its meanings. And whoever does not follow their path, then he is speaking based on his opinion. And whoever speaks from his opinion, and from what he thinks Allaah’s Religion is, not getting that from the Book, he is in fact sinning (!), even if he may be correct. Whereas whoever takes from the Book and the Sunnah, he is rewarded even if he errs. However, if he is correct, his reward is multiplied.”
Then he said (pg. 217):
“So it is an obligation to completely submit to the Messenger صلى الله عليه وسلم, follow his orders, and meet his reports with acceptance and firm belief, without contradicting that by false notions that we consider “reasonable” or that constitute a misconception and doubt. Or that we put before it the views of men and the rubbish held in their minds. So we must single the Prophet صلى الله عليه وسلم out with regard to making him the judge, submitting to him, obeying him and complying with him, just as we single out the One who sent him in worship, humility, submissiveness, repentance and reliance (to Him).”
In summary: It is an obligation upon all of the Muslims to not differentiate between the Qur’aan and the Sunnah, with regard to the obligation of accepting both of them together and establishing Laws based on both of them. Indeed this is the guarantee that will prevent them from drifting to the right and the left, and from returning to deviation.
This is as the Prophet صلى الله عليه وسلم clearly stated:
“I have left two things for you, which you will never go astray so long as you adhere to them: The Book of Allaah and my Sunnah. These two will never separate from one another until they return to the Fountain.”
[Reported by Maalik and Al-Haakim with a sound chain of narration]
 We do not say as is the custom amongst many of the people of knowledge: “We interpret the Qur’aan by the Qur’aan if there is no trace of it in the Sunnah, then we interpret it by the Sunnah.” This is due to what we will explain later on in the end of this treatise, when speaking about the (weak) hadeeth of Mu’aadh bin Jabal radhi Allaahu anhu.