Sahih Bukhari | Volume 7 | Hadith Number 673

Narrated by Abu Huraira
Allah's Apostle said, "If a fly falls in the vessel of any of you, let him dip all of it (into the vessel) and then throw it away, for in one of its wings there is a disease and in the other there is healing (antidote for it) i.e. the treatment for that disease."