Abdul-Rahman bin Abdullah bin Kaab bin Malik reported,

One of those who was present with the Prophet ﷺ at Khaybar reported that the Messenger of Allah ﷺ said about one of the men with him, "This man is among the people of the Fire."When the fighting began, the man fought with great intensity until he sustained many wounds. Some men from among the companions of the Prophet ﷺ came to him and said, "Messenger of Allah, what do you say about the man you mentioned as being among the people of the Fire? By Allah, he has fought fiercely in the cause of Allah and has suffered many wounds."The Messenger of Allah ﷺ replied, "He is indeed among the people of the Fire."Some of the people were almost overcome with doubt. While they were in this state, the man felt the pain of his wounds, reached his hand into his quiver, drew out an arrow, and killed himself with it.A man from the Muslims rushed to the Messenger of Allah ﷺ and said, "Prophet of Allah, Allah has confirmed the truth of your words. So-and-so has taken his own life and killed himself."

عن عبد الرحمن بن عبد الله بن كعب بن مالك

أنه أخبره بعض من شهد النبي ﷺ بخيبر أن رسول الله ﷺ قال لرجل ممن معه: إن هذا لمن أهل النار فلما حضر القتال، قاتل الرجل أشد القتال، حتى كثرت به الجراح، فأتاه رجال من أصحاب النبي ﷺ، فقالوا: يا رسول الله ﷺ، أرأيت الرجل الذي ذكرت أنه من أهل النار، فقد- والله- قاتل في سبيل الله أشد القتال، وكثرت به الجراح، فقال رسول الله ﷺ: إما إنه من أهل النار وكاد بعض الناس أن يرتاب، فبينما هم على ذلك وجد الرجل ألم الجراح، فأهوى بيده إلى كنانته، فانتزع منها سهما، فانتحر به، فاشتد رجل من المسلمين إلى رسول الله ﷺ فقال: يا نبي الله، قد صدق الله حديثك، قد انتحر فلان، فقتل نفسه.