Hadith: The martyrs are five: the one who dies from plague, who dies from an abdominal disease, who drowns, who dies because debris fell on him, and the one who dies fighting in the cause of Allah

عن أبي هريرة رضي الله عنه قالَ: قالَ رَسُولُ اللَّه -صَلّى اللهُ عَلَيْهِ وسَلَّم-: «الشهداء خمسة: المطعون والمبطون، والغريق، وصاحب الهَدْمِ، والشهيد في سبيل الله». وفي رواية «ما تَعُدُّونَ الشهداء فيكم؟» قالوا: يا رسول الله، من قتل في سبيل الله فهو شهيد. قال: «إن شهداء أمتي إذا لقليل» قالوا: فمن هم يا رسول الله؟ قال: «من قتل في سبيل الله فهو شهيد، ومن مات في سبيل الله فهو شهيد، ومن مات في الطاعون فهو شهيد، ومن مات في البطن فهو شهيد، والغريق شهيد».
[صحيح] - [متفق عليه]

Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "The martyrs are five: the one who dies from a plague, the one who dies from an abdominal disease, the one who drowns, the one who dies because debris fell on him, and the one who dies fighting in the cause of Allah." In another narration, the Prophet (may Allah's peace and blessings be upon him) asked the Companions: "Who do you consider to be martyrs amongst you?" They replied: "The one who is killed fighting in the cause of Allah is a martyr." He said: "If so, then the martyrs among my Ummah would be few." The Companions asked: "O Messenger of Allah, then who are the martyrs?" He replied: "The one who is killed fighting in the cause of Allah is a martyr, the one who dies naturally in the cause of Allah is a martyr, the one who dies of a plague is a martyr, the one who dies of an abdominal ailment is a martyr, and the one who drowns is also a martyr."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

The martyrs, in general, are five: one who is afflicted with a plague (a deadly epidemic) and dies of it, one who dies from an ailment in his abdomen, one who dies from drowning provided that he went to the sea for a lawful purpose, one who dies from debris, such as a wall falling on him, one who is killed while fighting for the sake of Allah, which is the highest level of martyrdom, and also one who dies in the way of Allah but not in the physical fight. The first four martyrs mentioned are considered martyrs in the Hereafter, meaning that they are not subject to the rulings pertaining to martyrs in this worldly life, so their bodies are washed and funeral prayer is offered over them. The number of martyrs mentioned in the Hadīth is not all inclusive.