The Prophet ﷺ said, "Whoever stabs himself will be stabbing himself in the Fire, whoever throws himself down will be throwing himself down in the Fire, and whoever strangles himself will be strangling himself in the Fire."
حدثنا يحيى عن ابن عجلان عن أبي الزناد عن الأعرج
عن النبي ﷺ الذي يطعن نفسه إنما يطعنها في النار والذي يتقحم فيها يتقحم في النار والذي يخنق نفسه يخنقها في النار
Its isnad is sahih. Bukhari related it, 7/181, in "Medicine," "Drinking poison and medicine," and Muslim, 1/103 no. 109, in "Faith," "The severity of the prohibition against a person killing himself."