It is narrated from Sayyiduna Ka'b bin Malik (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said about a man that he was one of the people of the Fire. The people began to wait to see what would become of him, until on the day of Hunayn he fought fiercely and showed great bravery. The people told the Messenger of Allah (peace and blessings be upon him) about this, and he (peace and blessings be upon him) said: "He is one of the people of the Fire." The narrator said: Then the man was wounded, so he took an arrow from his quiver and slew himself. The people said: O Messenger of Allah! Allah has proven your words true. The Messenger of Allah (peace and blessings be upon him) said: "O Bilal! Stand up and announce that none will enter Paradise except a believer, and that Allah, the Mighty and Majestic, supports this religion even through a wicked man."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16220