Musnad Ahmad 30:3207

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from Sulayman, from Dhakwan, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever kills himself with a piece of iron, his piece of iron will be in his hand, stabbing his belly with it in the Fire of Hell, remaining therein eternally, forever. And whoever throws himself from a mountain and kills himself, he is in the Fire of Hell, throwing himself therein, remaining therein eternally, forever."