The Book of Faith (Kitab Al-Iman)
Muslim :: Book 1 : Hadith 199
It is narrated on the authority of Abu Huraira that the Messenger of Allah (may peace be upon him) observed: He who killed himself with steel (weapon) would be the eternal denizen of the Fire of Hell and he would have that weapon in his hand and would be thrusting that in his stomach for ever and ever, he who drank poison and killed himself would sip that in the Fire of Hell where he is doomed for ever and ever; and he who killed himself by falling from (the top of) a mountain would constantly fall in the Fire of Hell and would live there for ever and ever.