Musnad Abu Ya'la al-Mawsili 3:223

'Abd al-A'la ibn Hammad narrated to us, Dawud ibn 'Abd al-Rahman narrated to us, Abu 'Abd Allah Maslamah al-Razi narrated to us, from 'Abd al-Malik ibn Sufyan al-Thaqafi, from Abu Ja'far Muhammad ibn 'Ali, from Muhammad ibn al-Hanafiyyah, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, Allah loves the believing servant who is frequently tested and frequently repentant."