The Messenger of Allah (peace and blessings be upon him) had ordered that Sayyiduna Furat bin Hayyan (may Allah be pleased with him) be killed; he was a spy and an ally of Abu Sufyan. Then he passed by a circle of the Ansar and said: I am a Muslim. A man among them said: O Messenger of Allah, he says: I am a Muslim. The Messenger of Allah (peace and blessings be upon him) said: "Among you are men whose faith has become apparent to me; among them is Furat bin Hayyan."
Hadith Referenceالمعجم الكبير للطبراني / باب الفاء / 15922