It was a Sunnah of Prophet Muhammad (peace be upon him) to fast extra days during the year.
When Ramadan was over, He used to fast some specific days that he felt they have great blessings and virtues; some of such days are Mondays and Thursdays, six days of Shawwal, three days in each month, the white days…
Throughout his life, he make it a habit to fast these virtuous days and he advised his followers to follow suit.
He teaches us that the virtues of voluntary fasting are so huge. And the greatness of the reward is only known to Allah because He said that fasting is for Him and He will reward for it.
Here we cite some of the virtues that Prophet Muhammad (peace be upon him) mentioned:
Whoever fasts one day for the sake of Allah, Allah will move his face away from the Fire a distance of seventy autumns (years). (Ibn Majah)
And:
Whoever fasts for three days of each month, he has fasted for a whole lifetime.
Then he said: Allah has spoken the truth in His book: Whoever brings a good deed shall have ten times the like thereof to his credit. (An nasa’i)
The White Days
Many people are confused about the white days; some name them after the days of Shawwal, however the white days Prophet Muhammad mentions in many hadiths are the three days in the mid of every lunar month. They’re called ‘white days’ because the night is lit when the moon is in its full shape.
These days are 13th, 14th, and 15th of the hijri calendar which coincide June 17th, 18th, 19th.
Muslims are highly encouraged to fast during these days as instructed by Prophet Muhammad (peace be upon him)
Abu Dharr narrated that:
The Messenger of Allah (peace be upon him) commanded us to fast for three days of every month; that is on the days of the full moon; the 13th, 14th, and 15th (of the lunar month).’ (Related by An-Nasa’i and At-Tirmidhi and rendered authentic by Ibn Hibban)
As shown in the above hadith, fasting these days is highly recommended, so why not try to fast and get great rewards?