فَإِنِ ادَّعَى قَوْلَ أَحَدٍ مِنْ عُلَمَاءِ السَّلَفِ بِمَا زَعَمَ مِنْ إِدْخَالِ الشَّرِيطَةِ فِي تَثْبِيتِ الْخَبَرِ، طُولِبَ بِهِ، وَلَنْ يَجِدْ هُوَ وَلَا غَيْرُهُ إِلَى إِيجَادِهِ سَبِيلًا، وَإِنْ هُوَ ادَّعَى فِيمَا زَعَمَ دَلِيلًا يُحْتَجُّ بِهِ قِيلَ لَهُ: وَمَا ذَاكَ الدَّلِيلُ؟
Translation: If the opponent attributes the additional condition to an early scholar, Muslim calls for proof of that attribution and maintains that none can be found. If the opponent claims an evidentiary argument, he is asked to identify the argument itself.
Al-Nawawī separately records competing theories of solitary reports: the majority require acting upon a qualified reliable report without generally treating it as necessary certainty; some groups disputed its binding authority; some Muʿtazilīs required two-by-two or four-by-four transmissions; certain hadith scholars asserted that such reports yield knowledge, and some made special epistemic claims for reports in the Ṣaḥīḥayn. Nawawī does not equate proof for action with absolute certainty.
Majority’s evidence: the Prophet sent individual envoys whose messages had to be followed, and the Companions acted upon reliable individual testimony in rulings, judgments and legal opinions, at times revising an earlier ruling on its basis. Such practice supports practical authority, not a claim that every āḥād report is as epistemically conclusive as mutawātir evidence despite possible error or forgetfulness.
This is Nawawī’s legal-theoretical discussion, not a speech by Muslim. Muslim’s direct question here concerns the specific **extra proof-of-meeting condition**.