النهي عن النفخ في الإناء
A prohibition on breathing into a cup while drinking from it or blowing directly onto food or drink to cool it.
نَهَى أَنْ يُتَنَفَّسَ فِي الْإِنَاءِ أَوْ يُنْفَخَ فِيهِ
“He forbade breathing into a vessel [while drinking] or blowing into it.” (meaning, not a literal translation)
This pairs naturally with the drinking-in-sips entry elsewhere on this site: the recommended method is to remove the cup from the mouth entirely between sips, breathing away from the vessel, rather than breathing directly into it as one drinks.
Commentators read this straightforwardly as hygiene — avoiding the transfer of saliva and breath-borne particles into shared food and drink, a principle modern food safety fully endorses. Ibn al-Qayyim groups this with other vessel-related hygiene instructions in the tradition, treating protection of shared food and drink as a recurring practical theme.
Modern food safety guidance similarly discourages blowing on hot food to cool it or breathing directly into shared containers, for the same underlying reason — reducing the transfer of respiratory droplets into something others will consume.