Sahih Muslim Book 1, Hadith Number 202.

Chapter : Suicide is the gravest sin.

It is narrated on the authority of Thabit b. al-Dahhak that the Apostle of Allah (may peace be upon him) observes: None is obliged to give votive offering (of a thing) which is not in his possession and the cursing of a believer is tantamount to killing him, and he who killed himself with a thing in this world would be tormented with that (very thing) on the Day of Resurrection, and he who made a false claim to increase(his wealth), Allah would make no addition but that of paucity, and he who perjured would earn the wrath of God