Sunan Ibn Majah 2804
سنن ابن ماجه#2804SahihIt was narrated from Abu Hurairah that the Prophet (ﷺ) said:“What do you say among yourselves about the martyr?” They said: “The one who is killed in the cause of Allah.” He said: “In that case the martyrs among my nation would be few. Whoever is killed in the cause of Allah is a martyr; whoever dies in the cause of Allah is a martyr; whoever dies of a stomach disease is a martyr; and whoever dies of the plague is a martyr.” Another chain narrates with the addition of "and the drowned is a martyr
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 24:52