From the perfection of the guidance of the last and final Messenger, Muḥammad (صلى الله عليه وسلم)—which includes matters of health—is the prohibition indicated in the following ḥadīths:
Imām al-Bukhārī narrates through Abū Qatādah from his father that the Prophet (صلى الله عليه وسلم) said: “When one of you drinks (from a vessel), let him not breathe into it.” It is also related by Muslim, al-Tirmidhī.
And Abū Dāwūd narrated through Ibn ʿAbbās who said: “The Messenger of Allāh (صلى الله عليه وسلم) prohibited from breathing into a vessel or blowing into it.”
And Ibn Mājah relates also from Ibn ʿAbbās: “The Messenger of Allāh (صلى الله عليه وسلم) never used to blow onto [his] drink.” This route is weak but it is raised due to other supporting narrations.
Benefits from this ḥadīth:
The prohibition of breathing in a vessel (of drink) or blowing onto it comprises the following affairs:
This action makes others averse from drink because souls are averse by their nature from drinking after someone has breathed into the vessel or blowed onto drink.
Breathing or blowing into a vessel leads to bacterial organisms from the mouth and nose to enter into the drink, and this can be a route of development (from afresh) or the transmission of disease conditions.
This practice involves resembling the animals, and thus, opposes good etiquette and nobility of manners.
This indicates that there is a method through which one should drink from vessels in order to comply with this prohibition.