The Messenger of Allah ﷺ said, "When a fly falls into one of your vessels, dip it in completely, then throw it out, for in one of its wings there is a cure and in the other there is a disease."
أن رسول الله ﷺ قال: إذا وقع الذباب إناء أحدكم فليغمسه كله، ثم ليطرحه فإن في إحدى جناحيه شفاء، وفي الآخر داء.
Bukhari related it in Medicine (5782) from Qutayba, who said, Ismail bin Jafar told us, from Utba bin Muslim, the freed slave of Banu Taym, from Ubayd bin Hunayn, the freed slave of Banu Zurayq, from Abu Hurairah, and he mentioned it.Ahmad (7141) and others related it through another route from Abu Hurairah, and they added to it, "and it protects with its wing the one that contains the disease, so let him dip it entirely." Ibn Ajlan is in this chain, and in my view he is hasan al-hadith unless he narrates alone or contradicts others, and he has narrated this addition alone.