Praise be to Allah.
As we celebrate Aidilfitri and bask in the festivities (bearing in mind the safety measurements in this Covid period), there is one special sunnah of fasting which only presents itself in this joyous month - it is the Sunnah of fasting the six days in Shawwal. Prophet Muhammad s.a.w. mentioned:
مَنْ صَامَ رَمَضَانَ ثُمَّ أَتْبَعَهُ سِتًّا مِنْ شَوَّالٍ كَانَ كَصِيَامِ الدَّهْرِ
“Fasting in Ramadan and following it with six days in Shawwal is like continual fasting.”
Scholars have explained that the reward of actions is multiplied by at least ten-fold. Based on the statement above, fasting in Ramadan for thirty days is equivalent to fasting three hundred days, and the six days of Shawwal is akin to fasting for sixty days. Our beloved Prophet Muhammad s.a.w. himself stated this explicitly:
صيامُ شَهرِ رَمَضانَ بِعَشرةِ أشهُرٍ، وسِتَّةُ أيَّامٍ بَعْدهُنَّ بِشَهرينِ، فذلك تمامُ سَنَةٍ
“Fasting Ramadan is like fasting ten months, and fasting six days (of Shawwal) is like fasting for two months. That is like fasting a full year.”
It is encouraged for Muslims to fast the six days in Shawwal consecutively as it provides greater reward and virtue in it. Based on the hadith narrated by Imam al-Tabarani and others, it is reported that the Prophet s.a.w. said:
مَنْ صَامَ سِتَّةَ أَيَّامٍ بَعْدَ الْفِطْرِ كَانَ تَمَامَ السَّنَةِ
“Fasting six consecutive days after Aidilfitri is like fasting the entire year.”
However, if someone is unable to do so, it is still valid to fast gradually for as long as it is observed within the month of Shawwal.
It is valid to combine the intention of making up missed fasts (Qadha') during Ramadan and the Sunnah of fasting the six days in Shawwal, though performing both separately would lead to a greater reward. This is as mentioned by Al-Hafidz As-Suyuthi in his book, Al-Asybah wa al-Nadhair, where he cited this to the position of al-Bariziy. However, you would need to make the intention that this fast is primarily intended to make up for the missed fast, and the fast of six days of Shawwal is only a supplementary one.
It is for this reason that Imam Ar-Ramli in his book Nihayatul Minhaj ila Syarh al-Minhaj stated that while it is permissible to combine both fasts, example, missed fasts of Ramadan and the fast of six days in Shawwal, the reward would be as comparable with the one who fasts separately where they will naturally gain more rewards.
On the other hand, Scholar like Sheikh Ali Gom’ah who opines that the hadith of fasting six days of Shawwal is general and as long as you have fasted 6 days in Shawwal whether, for the primary purpose of repaying missed fasts or for any of the sunnah fasts, you have obtained the reward of fasting six days of Shawwal.
Regardless of any views that we opt for, we should accept others adopting a different opinion on this matter. Any opinions that is based on scholarly Ijtihad has goodness in them, In sya Allah.
and Allah knows best.