My father fasts every year after Ramadan; he fasts six days and calls them al-Sittat. What is the ruling on this?

Question:
My father fasts every year after Ramadan; he fasts six days and calls them al-Sittud. What is the ruling on this?

Answer:
A person fasts only the days for which fasting is prescribed. The obligatory fast is the fast of Ramadan, and anything beyond that is voluntary. One fasts six days in Shawwal, one fasts Monday and Thursday of every week, one fasts three days of every month, one fasts the Day of 'Arafah, one fasts the month of Muharram, with emphasis on the tenth, which is the Day of 'Ashura, the day before it, and the day after it. These are the days for which fasting is recommended. As for anything other than that, it is not prescribed. Yes. May Allah reward you with good.