السلام عليكم ورحمة الله وبركاته
1. Virtue of Fasting the Six Days of Shawwāl
1.1. The Messenger ﷺ said: “Whoever fasts the Month of Ramaḍān and follows it with the Six days of Shawwāl, it is as if he observed fasting for the whole year” [Muslim].
1.2. We strongly encourage our community to uphold and observe this blessed Sunnah.
2. Timing for Fasting: Immediate or Spaced Out
2.1. The Shafi’ī school agree that it may be done spaced out throughout the month of Shawwāl without compunction. However, it is more encouraged to observe it consecutively, following the day of Eid.
3. Priority between Fasting Qaḍā’ or Six days
3.1. If one intends on separating the Qaḍā’ fast from the Six days of Shawwāl, then Qaḍā’ should be given preference.
3.2. Whether or not it is recommended or compulsory to give preference to the Qaḍā’ depends on the following:
3.2.1. If one had missed a day of fasting with an excusable reason, then it is recommended to give preference to the Qaḍā’;
3.2.2. If it was without an excusable reason then it is compulsory to complete the Qaḍā’ first before starting the Six days.
4. Combining the Fast of Qaḍā’ with the Six days
4.1. The fuqahā’ unanimously agree that separating the Qaḍā’ fast from the Six days of Shawwāl is the optimal approach. This is the only way to ensure that one achieves the reward mentioned in the ḥadīth.
4.2. Whether or not one may combine them, our Shafi’ī fuqahā’ differ:
4.2.1. The official view states that one may combine both with a dual intention, however, one will not have achieved the full reward mentioned in the ḥadīth, which is the reward of a full year of compulsory fast. What will be achieved in this instance is the Qaḍā’ fast and the mere adherence to the Sunnah (Aṣl al-Sunnah).
4.2.2. A contending view states that it must be observed separately, and cannot be combined at all.
5. Notwithstanding the above, we encourage our community to observe them separately if they are able to do so.
والله تعالى أعلم
And Allah knows best