The first one to be known that he debated with the rejecters of the Sunnah, sustained the argument with them and the response to them, is Imam Ash-Shaafi’i - may Allah have mercy on him - he mentioned in his main book (Kitaab Jamaa’ Al-‘Ilm, the chapter pertaining to the story of the saying of the party who rejected all reports). Ash-Shaafi’i mentioned there a dialogue, which took place between him and a member of this band (who is ascribed to be knowledgeable in the doctrine of his fellows).
And here is the summary of the argument of those who rejected all reports, as told by Ash-Shaafi’i about them: that the Quran came to explain everything. When the Hadiths brought new provisions, which were not in the Quran, that was in opposition from the presumptive proof, which are the Hadiths, to the peremptory proof, which is the Quran; and the presumptive does not have the strength to oppose the peremtory. When the Sunnah came to confirm the rule of the Quran, the following was for the Quran and not for the Sunnah. When it came to elucidate that which the Quran summed up, that was to elucidate the peremptory, which renders infidel the one who denies a single letter from it, by means of the presumptive, which renders infidel the one who denies its confirmation, and thus it is incumbent that they accept the Hadiths if they were recurrent, because they imply the definite by their confirmation. They, however, do not admit them as axioms, for they are rather presumptive for them too, because they came from single presumptive methods; so the probability of lying in their narration stands, even if they were a great crowd) (1).
The answer of Imam Shafi'i – may Allah have mercy on him – about the suspicions of those can be summarized as follows:
1 - That Allah has enjoined upon us to follow His Messenger and this is universal including those who were in his time, and all that will come after that. There is no way to that for those who had not seen the Prophet - peace be upon him – except through the Hadiths, so Allah Has commanded us to follow them and accept them, because that which the duty is not complete without it, is a duty.
2 – That there must be acceptance of the Hadith in order to know the provisions of the Quran itself, for the abrogating (provisions) and the abrogated (provisions) can only be known by reference to the Sunnah.
3 - That there are provisions agreed upon among all scholars and Muslim communities as a whole, even those who deny the probativeness of the Sunnah, and that is such as the number of obligatory prayers, the number of their rak'ahs, the minimum amount of possession liable for payment of the Zakat (Almsgiving) and others. There was no way of knowing them and proving them, except from the Sunnah.
4 - That the legislation had come to specify the peremptory with a presumptive, as in the testimony on murder and wealth, for the sanctity of the self and wealth are unequivocal. The testimony of two (people) has been accepted in them, and is presumptive without argument.
5 - That the reports, even though they may admit mistakes, illusion and lies, but the eventuality following ascertainment, the sureness about the uprightness of the narrator, comparing the narratives with accounts of his fellow narrators has become less than the probability stated in testimonies, particularly if the backup of the narrative is a text from the Book or the Sunnah, then the probability would be non-existent.
6 - Ash-Shaafi’i – may Allah the Almighty have mercy on him - did not mention, in this emplacement, the answer to their saying: Allah revealed the Book as explanation to everything, and mentioned it in many emplacements of his book Ar-Risaalah.
His answer was: that Allah did not make mention in the book about each of the subsets of the Law, but elucidated the fundamentals of the Law, its sources, regulations and general principles. Among the fundamentals He elucidated: the necessity to practice the Sunnah of the Prophet, peace be upon him, as in the verse: (So take what the Apostle assigns to you, and deny yourselves that which he withholds from you) (2).
From the opening chapter of the book (Ar-Risaalah) by Imam Ash-Shaafi’i, he finds that he responded lengthily to those who refuse argue by the Sunnah, or parts of it, like those who refused to argue by reports from single narrators (3).
(1) – Consult Kitaabul Umm (7/250). See also: Defense of the Prophetic Hadith, p. 101, Al-Adhwaa’ As-Sunniyyah ‘Ala Madhaahib Raafidhiy Al-Ihtijaaj Bissunnah Annabawiyyah p.24, 25 and following pages.
(2) – Surah Al Hashr, 7.
(3) - See: Al-Adhwaa’ As-Sunniyyah, p. 27.