Sayyiduna Umar bin Khattab (may Allah be pleased with him) narrates: When, on the occasion of the Battle of Khaybar, some people from among the companions of the Prophet (peace and blessings of Allah be upon him) were martyred, the people said: So-and-so is a martyr, so-and-so is a martyr, until they mentioned a certain person and said: That so-and-so is a martyr. Then the Prophet (peace and blessings of Allah be upon him) said: Never! I saw him in the Hellfire because of a cloak (the narrator is in doubt, perhaps these are the words) or a sheet which he had acquired deceitfully. Then the Prophet (peace and blessings of Allah be upon him) said: O son of Khattab, go and announce among the people that only a believer will enter Paradise. Sayyiduna Umar (may Allah be pleased with him) narrates: I left from there and made this announcement among the people.
Hadith Referenceصحیح ابن حبان / كتاب السير / 4849
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح: م.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده حسن على شرط مسلم