وأما خبر الواحد فلم يفد العلم
A non-mass-transmitted report, considered in itself, does not yield this degree of certainty.
Khabar al-wāḥid includes reports not meeting tawātur, not necessarily reports by only one narrator. Its acceptance and practical legal authority are distinct from the question of what produces conclusive knowledge.
Corroborating circumstances can strengthen a report's epistemic force. Thus neither “all non-mutawātir reports are equally worthless” nor “every sound isolated report automatically has the certainty of tawātur” accurately captures the distinction under discussion.