Hadith 764

Abu Sa'id Al-Khudri (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) 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 (PBUH) replied, "Pour them out." Then the man said: "My thirst is not quenched with one draught." Messenger of Allah (PBUH) said, "Then put away the cup from your mouth (in between three gulps), and take breath."

[At-Tirmidhi].