Warning about a hadith with no basis, namely: "The leftover drink of a believer is a cure."

The Shaykh : Incidentally, we should point out—since we are discussing the leftover drink of a human being—a hadith that is widespread among people, which says: "The leftover drink of a believer is a cure." Our research was to dispel a misconception that may arise in some minds, namely that the leftover drink of a person might be ritually impure. We dispelled this misconception by citing the consensus of the Muslims that the leftover drink of a human being is pure, as detailed previously. However, there is a superstition contrary to this matter; it is that this leftover drink is not only pure, but it is a cure if it is from a specific type of the human species, namely the believer: "The leftover drink of a believer is a cure." This hadith has no basis. This hadith is not authentic, and it has not been reported at all from the Messenger of Allah (peace and blessings be upon him), nor with a fabricated chain of narration. It is something that has no basis whatsoever. Therefore, it is not permissible to describe the leftover drink of a believer with a characteristic that has not been established scientifically, neither in the science of the Shari'ah nor in the science of medicine. Otherwise, if we say that, we would be saying and stopping at something about which we have no knowledge. And Allah (Mighty and Majestic) says: . Therefore, it is not permissible for us to attribute to Allah what is not true and say: "The leftover drink of a believer is a cure." And this, unfortunately, is a prevailing superstition. "The leftover drink of a believer is a cure" is something we often hear on some occasions.
On the contrary to this, some people are obsessed, and if you wish, I would say obsessed with what is in them of selfishness or arrogance, or they have knowledge of some of the principles of medicine, so they exaggerated in these principles. This led them to refrain from drinking from a cup in which a person has drunk, even if he is a Muslim believer, for fear that there might be a germ in it.

The questioner : All the Westerners.

The Shaykh : My master, the Westerners are a group of disbelievers, so there is nothing strange in that.

The questioner : And this is imitation of them.

The Shaykh : But some Muslims fell into this; they do not drink from a cup from which a believer has drunk, especially if he is a poor peasant, so their bodies and hair recoil from drinking from that cup out of arrogance on earth. This, too, is not permissible. And their matter has reached what is more than that; they did not stop at refraining from drinking the leftover drink of a believer. This is one of the misfortunes of humans: excess and deficiency. The leftover drink of a believer was a cure, and behold, it becomes a disease! For some, it is a cure, and behold, the matter turns around and becomes a disease. Neither this nor that.