"If a fly falls into the vessel of one of you, let him dip it in,"
The Book of al-Fara' and al-'Atirah - Sunan an-Nasa'i 4262
This narration from the Prophet Muhammad (peace be upon him) contains profound wisdom that appears contrary to conventional understanding, yet reveals divine knowledge of microbiology.
Scholarly Commentary
When the fly falls into liquid, it carries harmful bacteria on one wing and the antidote on the other. The command to fully immerse the fly allows the antidote wing to counteract the poison.
Imam Ibn Hajar al-Asqalani explains this demonstrates that Allah has created cures within creation itself, and the Prophet's instruction reveals knowledge beyond human comprehension at that time.
This hadith exemplifies the principle of trusting divine wisdom even when the reasoning isn't immediately apparent to human intellect.
Juridical Ruling
The majority of scholars consider this a recommended practice (mustahabb) rather than obligatory. The water remains pure and permissible to drink after dipping the fly completely.
This ruling applies specifically to flies falling into vessels of water or similar liquids where complete immersion is possible.