The Qur'an is very clear and its language is very plain, and the prophet (SAW) explained all the Qur'an. 

Every Muslim should accept a hadeeth if it is proved authentic. The four Imams agreed that the authentic Hadeeth is the authority and reject all sayings contrary to it. It is important to understand that all the four imams said to follow the Quran and Sunnah only, and not to follow them blindly. 

These are the clear, lucid sayings of the Imaams (Allaah Exalted be pleased with them) about sticking to the Hadeeth and forbidding the following of their opinion without clearly- visible evidence, such that mere opinion and interpretation is not acceptable.

Here are some of the statements on Hadeeth by the four Imams. 

1. "When a hadeeth is found to be saheeh, then that is my madhhab."

2. "It is not permitted for anyone to accept our views if they do not know from where we got them."

In one narration, "It is prohibited for someone who does not know my evidence to give verdicts on the basis of my words."

Another narration adds, "... for we are mortals: we say one thing one day, and take it back the next day."

In another narration, "Woe to you, O Ya'qub (Imaam Abu Haneefah's illustrious student, Abu Yoosuf)! Do not write down everything you hear from me, for it happens that I hold one opinion today and reject it tomorrow, or hold one opinion tomorrow and reject it the day after tomorrow."

3. "When I say something contradicting the Book of Allaah the Exalted or what is narrated from the Messenger (sallallaahu 'alaihi wa sallam), then ignore my saying."

1. "Truly I am only a mortal: I make mistakes (sometimes) and I am correct (sometimes). Therefore, look into my opinions: all that agrees with the Book and the Sunnah, accept it; and all that does not agree with the Book and the Sunnah, ignore it."

2. "Everyone after the Prophet (sallallaahu 'alaihi wa sallam) will have his sayings accepted and rejected - not so the Prophet (sallallaahu 'alaihi wa sallam)."

3. Ibn Wahb said: "I heard Maalik being asked about cleaning between the toes during ablution. He said, 'The people do not have to do that.' I did not approach him until the crowd had lessened, when I said to him, 'We know of a sunnah about that.' He said, 'What is that ?' I said, 'Laith ibn Sa'd, Ibn Lahee'ah and 'Amr ibn al-Haarith narrated to us from Yazeed ibn 'Amr al-Ma'aafiri from Abu 'Abdur-Rahman al-Hubuli from Mustawrid ibn Shaddaad al-Qurashi who said, 'I saw the Messenger of Allaah (sallallaahu 'alaihi wa sallam) rubbing between his toes with his little finger.' He said, 'This hadeeth is sound; I had not heard of it at all until now.' Afterwards, I heard him being asked about the same thing, on which he ordered cleaning between the toes."

1. "The sunnahs of the Messenger of Allaah (sallallaahu 'alaihi wa sallam) reach, as well as escape from, every one of us. So whenever I voice my opinion, or formulate a principle, where something contrary to my view exists on the authority of the Messenger of Allaah (sallallaahu 'alaihi wa sallam), then the correct view is what the Messenger of Allaah (sallallaahu 'alaihi wa sallam) has said, and it is my view."

2. "The Muslims are unanimously agreed that if a sunnah of the Messenger of Allaah (sallallaahu 'alaihi wa sallam) is made clear to someone, it is not permitted for him to leave it for the saying of anyone else."

3. "If you find in my writings something different to the Sunnah of the Messenger of Allaah (sallallaahu 'alaihi wa sallam), then speak on the basis of the Sunnah of the Messenger of Allaah (sallallaahu 'alaihi wa sallam), and leave what I have said."

In one narration: "... then follow it (the Sunnah), and do not look sideways at anyone else's saying."

4. "When a hadeeth is found to be saheeh, then that is my madhhab."

5. "You (Ahmed Ibn Hanbal) are more knowledgeable about Hadeeth than I, so when a hadeeth is saheeh, inform me of it, whether it is from Kufah, Basrah or Syria, so that I may take the view of the hadeeth, as long as it is saheeh."

6. "In every issue where the people of narration find a report from the Messenger of Allaah (sallallaahu 'alaihi wa sallam) to be saheeh which is contrary to what I have said, then I take my saying back, whether during my life or after my death."

7. "If you see me saying something, and contrary to it is authentically-reported from the Prophet (sallallaahu 'alaihi wa sallam), then know that my intelligence has departed."

8. "For everything I say, if there is something authentic from the Prophet (sallallaahu 'alaihi wa sallam) contrary to my saying, then the hadeeth of the Prophet (sallallaahu 'alaihi wa sallam) comes first, so do not follow my opinion."

9. "Every statement on the authority of the Prophet (sallallaahu 'alaihi wa sallam) is also my view, even if you do not hear it from me."

1. "Do not follow my opinion; neither follow the opinion of Maalik, nor Shaafi'i, nor Awzaa'i, nor Thawri, but take from where they took."

In one narration: "Do not copy your Deen from anyone of these, but whatever comes from the Prophet (sallallaahu 'alaihi wa sallam) and his Companions, take it; next are their Successors, where a man has a choice."

2. "The opinion of Awzaa'i, the opinion of Maalik, the opinion of Abu Haneefah: all of it is opinion, and it is all equal in my eyes. However, the proof is in the narrations (from the Prophet (sallallaahu 'alaihi wa sallam) and his Companions)."

3. "Whoever rejects a statement of the Messenger of Allaah (sallallaahu 'alaihi wa sallam) is on the brink of destruction."