In the practice of judging the sound from the spurious aḥādīth, the third criterion is the Qur’ān itself. In this regard the Prophet (sws) has been reported to have said:
Contradictory narratives (ascribed to me) shall soon reach you. Whatever of these accords with the Book of God and my Sunnah originates from me and whatever of it is against the Qur’ān and my Sunnah cannot be my word.
This ḥadīth gives us two principles. However, we shall confine our discussion on the status of the Qur’ān as the criterion and leave the Sunnah for the next section. The above ḥadīth teaches us to reject any such narrative as contradicting the Qur’ān in any aspect. On the discussion of the interrelationship of the Qur’ān, the Sunnah and the Ḥadīth, we have thoroughly discussed this issue. I explained that in matters of the religion the Qur’ān is the custodian over everything else and a criterion for distinguishing between truth and falsehood. Nothing contradicting it can ever be tolerated. Some extremist ahl al-Ḥadīth dare to posit that the Ḥadīth is custodian over the Qur’ān. Their view has been fully refuted in the light of the following saying of the most learned exponent of the Ḥadīth, Aḥmad b. Ḥanbal himself. It has been reported:
I heard Aḥmad b. Ḥanbal respond to a question regarding the traditions which say that the Sunnah overrules the Qur’ān: “I dare not say so. However, the Sunnah explicates the Book, defines and explains it.”
While referring to the status of the Qur’ān, as the criterion and distinguisher between the sound and unsound narratives, Khaṭīb Baghdādī writes:
A khabar-i wāḥid (an individual-to-individual report) shall not be accepted if it offends (manāfāt) commonsense, thābit and muḥkam (clear and established) Qur’ānic directives, the known Sunnah, the practice which is as current as the Sunnah and any definitive argument.
The word manāfāt employed by Khaṭīb connotes complete negation. Here I shall confine our discussion to the part of the statement that relates to the status of the Qur’ān in this regard. The aḥādīth which negate and contradict the Qur’ān are discarded. The reason is that the Qur’ān is the criterion for gauging everything in the religion for it is absolutely authentic and sound. As for the authenticity, it has been transmitted through qawlī tawātur (oral or documentary) of the ummah. This is why khabar-i wāḥid, the probable truth, cannot be acceptable if it goes against the Qur’ān. Khabar-i wāḥid can neither abrogate the Qur’ān nor change its directives nor affect its rulings and statements in any way.
(Translated from Islahi's Mabadi Tadabbur-i Hadith by Tariq Mahmood Hashmi)
Khatib Baghdadi, Al-Kifayah, 430.
This statement by Khaṭīb includes other important criteria which are taken up in the following discussions.