Musannaf Ibn Abi Shayba 33:986

'Abd al-Rahman narrated to us, he said: Abu Bakr ibn Abi Shayba narrated to us, he said: Ja'far ibn Sulayman narrated to us, he said: I heard 'Abd Rabbih Abu Ka'b saying: I heard al-Hasan saying: "Indeed, faith is not by adornment nor by wishful thinking. Indeed, faith is what settled in the heart and was verified by action."