A: It was authentically reported that the Messenger of Allah (peace be upon him) said: Anyone who fasts Ramadan and then follows it with six days of Shawwal it is as if they fasted the whole year. (Related by Imam Muslim in his Sahih [Authentic Hadith Book])These days are not fixed in the month. A Mu’min (believer) can choose to observe them at any time throughout the month, whether in the beginning, middle, or end of the month, and whether on separate or consecutive days. There is flexibility in this matter, praise be to Allah. If a person observes them in the beginning of the month, it will be even better, as this is a form of hastening to do good deeds. It is not thus, considered a Fard; a person can leave them in any year.
However, it is better and more perfect to continue observing Sawm on these days every year, acting on the saying of the Prophet (peace be upon him): The deed liked most by Allah is one to which the doer adheres constantly, even if it is small. May Allah grant us success!