From Sahih Muslim (Hadith 4930):
It has been reported on the authority of Sahl b. Aba Umama b. Sahl b. Hunaif who learned the tradition from his father who (in turn) learned it from his grandfather-that the Messenger of Allah (ﷺ) said:Who sought martyrdom with sincerity will be ranked by Allah among the martyrs even if he died on his bed. In his version of the tradition Abd Tahir did not mention the words:" with sincerity
Reference: Muslim 4930