Mishkat al-Masabih 20 Game and Animals Which May Be Slaughtered كتاب الصيد والذبائح 51

وَعَنْ أَبِي هُرَيْرَةَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذَا وَقَعَ الذُّبَابُ فِي إِناءِ أحدِكم فَلْيَغْمِسْهُ كُلَّهُ ثُمَّ لِيَطْرَحْهُ فَإِنَّ فِي أَحَدِ جَنَاحَيْهِ شِفَاءً وَفِي الْآخَرِ دَاءً» . رَوَاهُ الْبُخَارِيُّ

Abu Huraira reported God’s messsenger as saying, “When a fly alights in anyone’s vessel he should plunge it all in and then throw it away, for in one of its wings there is a cure and in the other disease.” Bukhari transmitted it.