Bukhari

Hadith Footnote:
Plague begins with a swelling that appears in the armpit or neck, which causes fever, and the person soon dies from it.
Allah protect us, Ameen.

Hadith Commentary:
(1)
The plague begins with a boil that appears under the armpit or on the neck; it causes fever, and a person quickly succumbs to death. A painful disease like the plague comes about in this world through its natural causes, but for the Ummah of the Messenger of Allah (sallallahu alayhi wa sallam), this disease has been made a source of mercy, subject to a few conditions:
➊ When the plague comes to one's city, one should not flee from there out of fear, because fleeing out of fear is contrary to steadfastness and trust in divine decree (qadar).
➋ If one remains in the city, one should do so with patience, not due to business or communal compulsion.
➌ While staying there, one should include the intention of seeking reward, because intention plays a major role in deeds.
➍ One should hold the belief that whatever Allah the Exalted has written in my destiny can neither be averted nor can one escape from it.
If, after fulfilling these conditions, death comes there, one will receive the reward of a martyr (shahid).

(2)
In any case, the belief in acceptance of divine decree (rida bil-qada) has very positive effects on a person's life, for example:
➊ By believing in predestination (qadar), calamities become easier for the servant, because all of this comes from Allah the Exalted. The believing servant considers these calamities as a test from Allah the Exalted and exercises patience.
➋ Through faith in qadar, a person always aspires to perform righteous deeds and seeks good character for his life, considering this to be the decree of destiny. Then he remains constantly engaged in the remembrance of Allah the Exalted.
➌ As a result of faith in qadar, correct actions are produced by the servant and good qualities develop; moreover, he takes risks in the path of truth for the support of the religion and encourages others to do so.
➍ Through faith in qadar, a person does not allow despair and hopelessness to come near him, nor does he embrace the curse of suicide at times of loss and distress.

(3)
Hafiz Ibn Hajar (rahimahullah) writes that Imam Bukhari's (rahimahullah) purpose in this hadith is that whatever hardship befalls a person has already been decreed by Allah the Exalted.
A person should exercise patience over it and hope for reward from Allah the Exalted.
(Fath al-Bari: 11/627)

Hadith Commentary:
➊
Allah has shown great mercy to this Ummah, because the disease that was imposed as a punishment upon previous nations has been made a source of mercy for this Ummah.
According to this hadith, dying from the plague (ta‘un) is considered minor martyrdom (shahadah sughra). Residing in a place afflicted by plague with the intention of seeking reward is also full of goodness and blessings. In the mentioned hadith, glad tidings of martyrdom have been given to such a person, even if he passes away after the time of plague due to some other illness.
➋
It is narrated from Abu Musa al-Ash‘ari (radi Allahu anhu) that during the time of plague, he would send his sons to the villages; perhaps this hadith had not reached him.
And Allah knows best.
(‘Umdat al-Qari: 11/228)

Hadith Commentary:
In the narration of Ibn Majah and Bayhaqi, it is stated that plague arises when immorality becomes widespread in a land.
Maulana Rumi has spoken the truth:
"Waz zina kheezad waba andar jihat."
For a Muslim, dying due to the plague holds the rank of martyrdom (shahadah), as mentioned in this hadith.

Hadith Commentary:
(1)
There are two conditions for becoming deserving of reward due to plague:
The first is that one remains in that place with patience and steadfastness, and does not flee to another location.
The second condition is that one remains content with the decree of Allah Ta'ala, and does not allow any kind of distress to enter his heart while staying there.
If he believes that by leaving this place he will attain salvation, then he will be deprived of the reward, even if he dies there due to the plague.
And if he possesses these qualities, then he will receive the reward of a martyr (shahid), even if he does not die due to the plague.
Under this, there are three scenarios:
٭ He possesses these qualities and dies there due to the plague.
٭ He is affected by the plague there, but does not die because of it.
٭ He is not affected by the plague and dies there due to some other cause.
(2)
In any case, a person who, with patience and hope for reward, does not leave a place where the plague has broken out, and does not die from the disease of the plague, will receive a reward similar to that of a martyr. And if he dies, then he is considered in the ruling of a martyr.
(Fath al-Bari: 10/238)