“If you hear of an outbreak of plague in a land, do not enter it; but if the plague breaks out in a place while you are in it, do not leave that place.” The Prophet (peace be upon him) said: “If you hear of an outbreak of plague in a land, do not enter it; but if the plague breaks out in a place while you are in it, do not leave that place.” (Reported by al-Bukhari and Muslim.)
Also, he (peace be upon him) said: “He who runs away from the place of plague is like the one running away from fighting in the cause of Allah; and he who is patient and stays where he is, he will be rewarded with the reward of a martyr.” (Reported by Ahmad.)
The Scientific Fact:
Modern science now understands the ways in which microorganisms multiply and the diseases they cause. Scientists affirm that healthy people who have no symptoms in the place of plague are already carrying the microbe and so they represent a real threat because they may transfer the plague to another place if they move to it.
Thus, this system of quarantine, in which all the people of the city that suffers from plague are prevented from leaving, and visitors are also prevented from entering, has now been established worldwide. In the 15th century, plague hit Europe causing the death of a quarter of its citizens. At that time, plagues and contagious diseases were much less in the Muslim world.
Facets of Scientific Inimitability:
At the time of the Prophet (peace be upon him) as well as before and after his time until Pasteur managed to discover the existence of microbes, people used to think that diseases were caused by devils, demons, and stars. That is they were not related to cleanliness or certain behaviors; thus, they resorted to sorcery and magic as a remedy.
In such an environment, the Prophet (peace be upon him) established the system of quarantine which is considered the basis of modern preventative medicine after the discovery of the microbes that cause diseases and plagues. The Prophet (peace be upon him) ordered his Companions: “If you hear of an outbreak of plague in a land, do not enter it; but if the plague breaks out in a place while you are in it, do not leave that place.” In order to make sure that his order would be carried out properly, he (peace be upon him) established a wall around the area of the plague and promised those who are patient and stay in the area of the plague with the reward of the martyrs, and those who run away from it were promised doom and perdition. Thus, he (peace be upon him) said: “He who runs away from the place of the plague is like the one running away from fighting in the cause of Allah and he who forbears it and stays where he is, he will be rewarded with the reward of a martyr.”
If a healthy person was asked two hundred years ago to stay with the sick people in a plague area, he would have considered this some kind of nonsense and in response to his desire to live he would have run away to another place. Only Muslims did not run away and leave at the time of plague in compliance with the order of the Prophet (peace be upon him). Non-Muslims mocked them for this act until it was later discovered that those who appear to be healthy with no symptoms, are the germ carriers who might transfer the plague to another place if they moved to it. They would move freely and mingle with healthy people, so they might cause them to catch the disease.
Who told the Prophet (peace be upon him) this fact? Could a human being know something like this fourteen centuries ago, or is it revelation from the All-Knowing, the Almighty Allah. Allah, the Almighty, says:
[And say, O Muhammad, to these polytheists and pagans, ‘All the praises and thanks be to Allah. He will show you His signs and you shall recognize them. And your Lord is not unaware of what you do.’] (An-Naml: 93)
Source: https://www.islamland.com/eng/articles/quarantine-a-prophetic-discover