Sahih Muslim Book 23, Hadith Number 5030.

Chapter : It is repugnant to breathe in a vessel and appreciable to breathe three times outside the vessel in course of drinking.

Anas reported that Allah’s Messenger (may peace be upon him) breathed three times (outside the vessel) in the course of a drink and said: It is more thirst-quenching, healthier and more wholesome. Anas said: So I also breathe three times in the course of a drink.