Abu Hurairah reported,

We were present with the Messenger of Allah ﷺ at Khaybar. The Messenger of Allah ﷺ said about one of the men with him who claimed to be a Muslim, "This man is among the people of the Fire."When the battle began, the man fought most fiercely and sustained many wounds that incapacitated him. One of the Prophet's companions came and said, "Messenger of Allah, do you realize that the man you said was among the people of the Fire has fought most fiercely in the cause of Allah and has been heavily wounded?"The Prophet ﷺ replied, "He is indeed among the people of the Fire."Some of the Muslims nearly began to doubt. While they were in that state, the man, feeling the pain of his wounds, reached for his quiver, drew out an arrow, and killed himself with it. Some men of the Muslims rushed to the Messenger of Allah ﷺ and said, "Messenger of Allah, Allah has confirmed your words. So-and-so has taken his own life."The Messenger of Allah ﷺ said, "Bilal, stand up and announce that none shall enter Paradise except a believer, and that Allah indeed supports this religion even by means of a wicked man."

عن أبي هريرة قال

شهدنا مع رسول الله ﷺ خيبر، فقال رسول الله ﷺ لرجل ممن معه يدعي الإسلام: هذا من أهل النار. فلما حضر القتال قاتل الرجل من أشد القتال، وكثرت به الجراح فأثبتته، فجاء رجل من أصحاب النبي ﷺ فقال: يا رسول الله، أرأيت الذي تحدثت أنه من أهل النار، قاتل في سبيل الله من أشد القتال، فكثرت به الجراح، فقال النبي ﷺ: أما إنه من أهل النار. فكاد بعض المسلمين يرتاب، فبينما هو على ذلك إذ وجد الرجل ألم الجراح، فأهوى بيده إلى كنانته فانتزع منها سهما فانتحر بها، فاشتد رجال من المسلمين إلى رسول الله ﷺ فقالوا: يا رسول الله صدق الله حديثك، قد انتحر فلان فقتل نفسه، فقال رسول الله ﷺ: يا بلال، قم فأذن لا يدخل الجنة إلا مؤمن وإن الله ليؤيد هذا الدين بالرجل الفاجر.