Did the Messenger of Allah (may Allah's peace and blessings be upon him) fast three days of each month?

Mu‘ādhah al-‘Adawiyah reported that she asked ‘Ā’ishah: “Did the Messenger of Allah (may Allah's peace and blessings be upon him) fast three days of each month?” ‘Ā’ishah replied: 'Yes.' i.e. this is the least number of days that he fasted. Mu‘ādhah further asked: “Which days of the month (or week) did he fast?” i.e. those three days were from the beginning, the middle or the end of the month, and were they consecutive or separate? ‘Ā’ishah replied: “It did not matter to him…” i.e.

He did not specify certain days of the month to fast, because the reward is granted with fasting any three days. This means that he fasted according to what he deemed convenient, since something might come up and prevent him from observing fasting, or perhaps he did it to show in a practical manner what is permissible, and either of these reasons is excellent concerning his right and status.