The Prophet ﷺ said, "If a fly falls into the drink of any of you, let him dip it in fully, for in one of its wings is a disease and in the other is a cure."Hammad and Habib bin Shaheed reported the same from Muhammad bin Sirin, from Abu Hurairah, from the Prophet ﷺ.
حدثنا الأسود بن عامر حدثنا حماد يعني ابن سلمة عن ثمامة
أن النبي ﷺ قال إذا وقع الذباب في إناء أحدكم فليغمسه فإن في أحد جناحيه داء وفي الآخر دواء قال حماد وحبيب بن الشهيد عن محمد بن سيرين عن أبي هريرة عن النبي ﷺ مثله
[Shakir: 8642(A)] Bukhari and Ibn Majah narrated it from Abu Hurairah, and Suyuti included it in Jami Saghir, and Abu Dawud and Nasai also narrated it, and it is of a high degree of authenticity. Our early scholars held that there is no rational objection to Allah combining both the disease and the cure in a single thing. Indeed, this is something observed, as with the bee, which produces from its mouth honey containing healing, while releasing poison from its lower end. Modern medicine has also discovered that the fly carries a substance that kills microbes, so that when it is dipped into a vessel, this substance becomes a means of destroying the germs it carries.8642 M, Hammad and Habib bin Shaheed said, from Muhammad bin Sirin, from Abu Hurairah, from the Prophet ﷺ, a similar report. [Shakir: 8642(B)]