What is the authenticity of the hadith: “When a fly falls into the drink of any of you, let him submerge it and then remove it”

The questioner : The hadith: Is this hadith authentic?

The Shaykh : Yes, it is authentic.

The questioner : ... knowing that the fly is impure and ... .

The Shaykh : The condition for contradiction is opposition on a specific point. That is, if the hadith said that the fly is not impure, and medicine says that it is impure, that would be the contradiction.

The questioner : Pardon me, but modern medicine has proven this.

The Shaykh : Pardon me, be quiet so that it is your turn to speak!
Now, the questioner is here, so that he may clear up the issue in his mind, and then others may speak.
The hadith does not contradict the medicine that says the fly is impure. But I feel that you have not clarified what medicine says about the fly. Because your statement that medicine rules that the fly is impure is not a matter for medicine. All people, whether doctors or not, whether educated or not, know that the fly is impure. This fact is indicated by the question of one of the Iraqis to 'Abd Allah ibn 'Umar ibn al-Khattab. He said to him: “O Ibn 'Umar, the fly falls on impurity, and then falls on my garment; what is your opinion, does my garment become impure?” Is this not a reference to its impurity? But Ibn 'Umar answered the questioner by saying: “O people of Iraq, you do not ask us about the small matter, and you ride us on the great matter! You killed al-Husayn, and now you ask about the fly falling in such a place, and then on such a garment?”
The point is that the fly being impure does not need medicine. This is known, what? Generally. So you mean something else. You mean that the fly, as medicine attests, is a carrier of germs, is that not so?

The questioner : It all puts things on impurities ... .

The Shaykh : No, I mean by my statement that a person should be precise in his expression. Because when you said “impure,” that is an impurity that does not need medicine. It is known to all people. But your later statement that because it is impure, it carries germs; that is the medical point that the general public does not know. As for the impurity, all people know it, even in a time when there was no medicine claiming that there are germs not visible to the naked eye, as Ibn 'Umar said to the questioner. Was there medicine in his time? The discovery of these small germs? Of course, there was not. But its being impure is known by observation.
The point is: the fact that medicine rules that the fly carries germs does not contradict the hadith. Because the hadith itself confirms this medical fact. Because it did not tell you: ? Yes, this disease is what medicine has acknowledged. So it does not contradict medicine. But the truth is that Prophetic medicine came with news from the revelation of the sky. Naturally, when medicine looks into it through experiment today, this is the truth. And if this is clarified to you, then the question is wrong. Because medicine today does not contradict the hadith nor oppose it. And that is why I began the answer when I replied to you by saying there is no contradiction. Because medicine, according to your previous expression, rules that the fly is impure. If the hadith had ruled that the fly is not impure, there would be what? A contradiction. Because the inquiry is about a specific point, negated and affirmed. That is how contradiction occurs.
But the truth is that the Prophetic hadith established a medical fact before medicine came with today’s experiment. And it established another fact that today’s medicine has not discovered. The first is the disease, the germs that the Messenger (peace be upon him) described as a disease. This was, of course, discovered by medicine centuries after the Messenger (peace be upon him). And this other fact, which is included in it and which the science of medicine has not yet come to know, is that there is a cure. That is, in the end, this is what medicine has not discovered. And the science of medicine, like all sciences, its scholars testify that the more they increase in knowledge, the more they increase in awareness of their ignorance, in accordance with the saying of Allah (Blessed and Exalted is He): . So does any scholar in any science say: “My knowledge has reached this point, and what I do not know is more than what I know”? Do you not agree with me that they say this?

The questioner : This statement is correct.

The Shaykh : So the Prophetic hadith came with a fact that medicine has not addressed, neither negatively nor positively. So it came with a fact that medicine has been ignorant of until today. It may discover it in the near or distant future. This is knowledge with Allah. Or it may not discover it at all, and this may be something that Allah (Mighty and Majestic) has kept to Himself. So there is no contradiction at all between the hadith of the fly and medicine.
Is it clear?
Please proceed.
...
[One of the attendees calls the adhan].

The Shaykh : If Abu Hamzah wants to sleep, he is excused. Because he was our driver for the length of the journey. But what is Abu 'Abd’s excuse for wanting to sleep?
[One of the attendees calls the adhan].

The Shaykh : Aloud? By mistake, I mean?

The questioner : I mean my prayer. I do not have to separate from ... .

The Shaykh : No, you do not have to separate.

The questioner : My prayer, I mean, do I have to repeat it?

The Shaykh : No, but you do not have to repeat what you did in your prayer.