Mu'jam Kabir Tabarani 11636 — one day the Prophet ﷺ said

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that one day the Prophet (peace and blessings be upon him) said to his Companions: "Whom do you consider to be martyrs among you?" The Companions said: Whoever is killed in the path of Allah, patient and seeking reward, advancing and not turning his back, is a martyr. He (peace and blessings be upon him) said: "Then the martyrs of my Ummah would be very few. The one killed in the path of Allah is a martyr; the one who dies on his bed in the path of Allah is a martyr; the one who dies of a disease of the stomach is a martyr; the one who is stung (or bitten) is a martyr; the one who drowns is a martyr; the one who dies of choking is a martyr; the one who is devoured by a wild beast is a martyr; the one who falls from his mount (and dies) is a martyr; the one who dies under a collapsing building is a martyr; the one who dies of pleurisy (dhat al-janb) is a martyr; and the woman in childbirth whose child kills her (is a martyr) - that child will pull her by its umbilical cord into Paradise."