Musnad Abu Ya'la al-Mawsili 151:3

Abu Khaythama narrated to us, Ibn 'Uyaynah narrated to us, 'Abd al-Karim al-Jazari narrated to us, from Ziyad ibn Abi Maryam, from 'Abd Allah ibn Ma'qil, who said: I entered with my father upon 'Abd Allah, and he said: I heard the Messenger of Allah, may Allah bless him and grant him peace, say: "Remorse is repentance." He said: Yes.