What are the days it is recommended to fast during the Hijri year?

The days when it is recommended to fast are: six days of Shawwal, the first nine days of Dhul-Hijjah (the first ten days), the Day of Arafah for those not performing Hajj, the days of Muharram and fasting Ashura along with adding the ninth day to it, the days of the month of Sha'ban, three days from every month—preferably the White Days (13th, 14th, and 15th)—and fasting on Mondays and Thursdays. It is better to consistently observe some of these, for the Prophet, peace and blessings be upon him, said: "When he performed an act, he made it firm."