Anas was asked about the voluntary fasting of the Messenger of Allah ﷺ. He said, "He used to fast until we would say he never breaks his fast, and he would go without fasting until we would say he never fasts."
حدثنا يحيى بن سعيد
سئل أنس عن صوم رسول الله ﷺ تطوعا قال كان يصوم حتى نقول لا يفطر ويفطر حتى نقول لا يصوم