We are now approaching the “White Days” of the blessed month of Dhu’l-Qa`dah, in sha Allah. The “White Days” are the days which follow nights in which the moon is full, namely the 13th, 14th and 15th days of each lunar month. The Messenger of Allah ﷺ encouraged his Companions to fast three days in every month and to fast these days specifically.
He said ﷺ: “If you fast three days in the month then fast the thirteenth, fourteenth and fifteenth” (Narrated by al-Tirmidhi and al-Nasa’ī). The reward for fasting these days in Dhu’l-Qa`dah will also be multiplied because it is a sacred month.
Sayyidi al-Habib `Umar bin Hafiz (may Allah preserve him and benefit us by him) encourages his students in Dar al-Mustafa to combine these two sunnahs. Please check the moon sighting in your locality to be sure that your fast coincides with the “White Days.”