Musnad Ahmad 2:246

Abu Sa’id narrated to us, ‘Ikrimah ibn ‘Ammar narrated to us, Abu Zumayl narrated to us, Ibn ‘Abbas narrated to me, ‘Umar ibn al-Khattab narrated to me, he said: When the day of Khaybar arrived, a group of the companions of the Messenger of Allah (peace and blessings of Allah be upon him) came forward saying: "So-and-so is a martyr, and so-and-so is a martyr," until they passed by a man, and they said: "So-and-so is a martyr." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Nay, I have seen him being dragged into the Fire in a cloak he had misappropriated." "Go out, O ‘Umar, and call out among the people: 'Indeed, none shall enter Paradise except the believers.'" So I went out and called out: "Indeed, none shall enter Paradise except the believers."