He should not return (from prayer) unless he hears a sound or perceives a smell (of passing wind). Abu Bakr and Zuhair b. Harb have pointed out in their narrations that it was 'Abdullah b. Zaid.
The Book of Menstruation - Sahih Muslim 361
This narration from Sahih Muslim addresses the important matter of doubt during prayer, specifically concerning the nullification of ablution. The hadith establishes that mere suspicion or uncertainty about having broken one's wudu is insufficient grounds to discontinue prayer. The Prophet (peace be upon him) instructed that a person should only cease prayer if they hear a sound or perceive a smell definitively indicating the passing of wind. This ruling prevents the frequent interruption of worship due to baseless doubts, which can be a form of whisperings from Satan. The clarification by narrators Abu Bakr and Zuhair b. Harb that this was Abdullah b. Zaid ensures the chain's authenticity and removes any ambiguity about the companion relating this guidance.
Scholarly Commentary
Islamic scholars from all madhahib (schools of jurisprudence) agree that certainty cannot be overruled by doubt. The principle derived from this hadith is that one's original state of purity remains valid until there is definitive evidence to the contrary. The requirement for either auditory or olfactory evidence provides objective criteria, preventing subjective doubts from invalidating acts of worship.
This teaching also addresses the spiritual aspect of waswas (devilish whisperings), which often manifests as excessive doubt in ritual purity. By establishing clear, tangible evidence requirements, the Shariah protects believers from this spiritual ailment and allows for uninterrupted devotion to Allah.