Is it permissible for a Muslim to fast every other day and at the same time fast on Mondays, Thursdays, the middle three days (13,14 and 15) of each lunar month and occasions where fasting is recommended ? Or should he restrict the fast to a specific manner such as fasting on every other day only, even though this might cause him to miss fasting days such as Mondays, Thursdays, and the three days of each lunar month?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

It has authentically been narrated on the authority of ‘Amr Ibn Al-‘Aas that the Prophet, sallallaahu ‘alayhi wa sallam, said to him: “Fast three days in every month.” He said, “I am able to offer more.” ‘Amr kept asking the Prophet, sallallaahu ‘alayhi wa sallam, to recommend him to observe more fasts until the Prophet, sallallaahu ‘alayhi wa sallam, said to him: “Fast every other day. Such is the fasting of Daawood (David) and it is the best plan to follow.” ‘Amr said, “But I am able to fast more than this.” The Prophet, sallallaahu ‘alayhi wa sallam, said to ‘Amr: “No fast is better than what I have just mentioned.” [Al-Bukhari and Muslim, with different wordings] This hadith indicates that fasting on every other day is the best and most beloved plan to Allaah, as authentically stated in the other narration.      

Also, the hadith explains that no other plan is better than this one even if the person is able to offer more. Nor would it be better for the Muslim to offer more fasts than the fasting of every other day, even if it involves no harm to himself or his family. This is because fasting more than this is less favorable, and what is better and more liked is that the person adheres only to the method of fasting followed by Prophet Daawood .

However, the question here is: what if a day whose fasting is enjoined by the Sunnah, such as the Day of ‘Arafah or the Day of ‘Aashooraa’, coincides with a non-fast day for a person who fasts every other day? Should that person strictly stick to his plan of fasting every other day or may he additionally fast the recommended day? Zakariyya Al-Ansaari, the Shafi‘i scholar said:

If a non-fast day of the person who fasts every other day coincides with a day that is recommended for fasting based on the Sunnah, like the Day of ‘Arafah or the Day of ‘Aashooraa’, then it is more recommended for that person to fast this additional recommended day. That person should note that fasting such a day never precludes his reward for fasting every other day.

Allaah Knows best.