Musnad Ahmad 466:1

Ya'qub narrated to us, he said: My father narrated to us, from Salih ibn Kaysan. Ibn Shihab said: Abd al-Rahman ibn Abd Allah ibn Ka'b ibn Malik informed me that some of those who witnessed the Prophet, peace and blessings of Allah be upon him, at Khaybar informed him that the Messenger of Allah, peace and blessings of Allah be upon him, said to a man who was with him: "Indeed, this one is among the people of the Fire." When the fighting began, the man fought the most intense fighting, until he was covered in wounds. Some of the companions of the Prophet, peace and blessings of Allah be upon him, came to him and said: "O Messenger of Allah, have you seen the man whom you mentioned was among the people of the Fire? By Allah, he has fought in the way of Allah the most intense fighting, and he has been covered in wounds." The Messenger of Allah, peace and blessings of Allah be upon him, said: "Verily, he is among the people of the Fire." Some of the people almost doubted. While they were in that state, the man felt the pain of his wounds, so he reached with his hand toward his quiver, pulled out an arrow from it, and committed suicide with it. A man from the Muslims rushed to the Messenger of Allah, peace and blessings of Allah be upon him, and said: "O Prophet of Allah, Allah has made your speech true; so-and-so has committed suicide and killed himself."