Mishkat al-Masabih #3646

Abu Huraira reported God's Messenger as saying, "God most high will cheerfully welcome two men one of whom kills the other. They will enter paradise, one having fought in God’s path and been killed, and the slayer, after receiving God's pardon, having died as a martyr."* * The man who had fought and killed a Muslim later became a Muslim himself and was killed in the course of jihad. (Bukhari and Muslim.)