Undesirability of blowing into the Vessel while Drinking

765. Abu Sa`id Al-Khudri (May Allah be pleased with him) reported: Messenger of Allah (sallallaahu ’alayhi wa sallam) prohibited us blowing in the drinking water. A man said: “O Messenger of Allah! Sometimes I see some litter floating about on the surface. What should I do then?” He (sallallaahu ’alayhi wa sallam) replied, “Pour them out.” Then the man said: “My thirst is not quenched with one draught.” Messenger of Allah (sallallaahu ’alayhi wa sallam) said, “Then put away the cup from your mouth (in between three gulps), and take breath.”
[At-Tirmidhi].

766. Ibn `Abbas (May Allah be pleased with them) reported: The Prophet (sallallaahu ’alayhi wa sallam) prohibited us from breathing into the drinking vessel or blowing onto.
[At-Tirmidhi].