Sayyiduna Salman (may Allah be pleased with him) narrated: I came to the Messenger of Allah (peace and blessings be upon him) with the zakah three times, and he (peace and blessings be upon him) said: "Whom do you count as a martyr among you?" The Companions said: The one who is killed in the path of Allah. He (peace and blessings be upon him) said: "Then the martyrs of my Ummah would be few. Being killed in the path of Allah is martyrdom, dying of plague is martyrdom, dying in childbirth is martyrdom, burning to death is martyrdom, drowning is martyrdom, tuberculosis is martyrdom, and dying of an abdominal disease is martyrdom."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6090