Sahl bin Hunaif (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "He who supplicates Allah sincerely for martyrdom, Allah will elevate him to the station of the martyrs, even if he dies on his bed."[Muslim].
App reference: Book 12, Hadith 37
Arabic/English book reference: Book 12, Hadith 1321