Hadith 4:840
Ghundar narrated to us, from Shu'bah, who said: I asked al-Hakam and Hammad about a man who fasts voluntarily, and his mother forbids him. He does not obey her and fasts sometimes.
حدثنا غندر عن شعبة قال سألت الحكم وحمادا عن الرجل يصوم تطوعا فنهته أمه فلا يطيعها ويصوم أحيانا