Abu Hurairah narrated (from the Messenger of Allah (s.a.w)):
"Whoever kills himself with (an instrument of)iron, he will come on the Day Of Judgment with his iron in his hand, to continually stab himself in his stomach with it, in the fire of Jahannam, dwelling in that state eternally. And whoever kills himself with poison, then his poison will be in his hand, to continually take it in the Fire of Jahannam, dwelling in that state eternally."
English reference: Vol. 4, Book 2, Hadith 2043
Arabic reference: Book 28, Hadith 2178