First and foremost The Holy Qur’an clearly sets out the prohibition of the taking of one’s own life i.e. suicide,
…And kill not yourselves. Surely Allah is Merciful to you. And whoso does that by way of transgression and injustice, We shall cast him into Fire; and that easy with Allah. (Ch.4: V.30-31)
Suicide amounts to nothing less than murder and is thus repulsive in Islam, which is a religion that champions the sanctity of life,
…whosoever killed a person – unless it be for killing a person or for creating disorder in the land – it shall be as if he killed all mankind; and whoso gave life to one , it shall be as if he had given life to all mankind.’’ (Ch.5: V.33)
The forbiddance of suicide is further observed in the saying of the Holy Prophet(sa),
‘… And whoever commits suicide with a piece of iron will be punished with the same piece of iron in the Hell Fire.” Narrated Jundab the Prophet said, “A man was inflicted with wounds and he committed suicide, and so Allah said: My slave has caused death on himself hurriedly, so I forbid Paradise for him.’ (Bukhari Vol. 2, Bk. 23, No. 445)
Suicide is therefore unconditionally forbidden. When it is used as a mechanism to murder others then it becomes an even greater sin. As a protest against intentional suicide the Holy Prophet(sa) has forbidden to observe funeral prayer for a person who commits suicide, [unless the person was mentally ill].