Jami` at-Tirmidhi Book 10, Hadith 104
"A man killed himself, so the Prophet did not perform Salat over him."
Aishah mentioned that the Messenger of Allah said: "Whoever loves to meet Allah, then Allah loves to meet him. And whoever dislikes meeting Allah, then Allah dislikes meeting him." She said: "O Messenger of Allah! All of us dislike death." He said: "It is not like that. But when the believer is given the good news of Allah's mercy, His pleasure, and His Paradise, then he loves to meet Allah and Allah loves to meet him. Whereas when the disbeliever is given the news of Allah's punishment and His wrath, he dislikes meeting Allah, and Allah dislikes meeting him."
The Prophet was brought a (deceased) man to perform Salat over. So the Prophet said: "Pray for your companion; for indeed he had a debt upon him." Abu Qatadah said: "It shall be upon me." So the Messenger of Allah said: "To pay it off?" (He said: "To pay it off.") So he performed the prayer for him.