Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
There are many Ahadith that tell the Muslim the best days to fast in, and here are the details:
- Six days from the month of Shawal as told by Abu Ayub (May blessings of Allah be upon him) that the Prophet (Sallallahu Alaihi wa Sallam) said: He who fasts Ramadan and follows it with six days of Shawal this is (as though) he fasted for one year. [Narrated by Ahmed , Abu Dawood and aI-Tirmizi ; Ahmed narration is from Jabir 's Hadith]
- The first ten days of Zil-Hijja as told by Hafsah (May blessings of Allah be upon her) that The Prophet (Sallallahu Alaihi wa Sallam) never refrained from doing four (things): Fasting of Ashura day, fasting the first ten days of the month of Zil-Hijja, fasting three days of every month, and (praying) the two Rak'ah before the dawn prayer. [Narrated by Ahmed and aI-Nasa'e ] The first ten days of Zil-Hijja means: The first nine days, because the tenth day is the I'd day and fasting it is forbidden. Also, only those who are not performing the Hajj are permitted to fast Arafah day, as told by Abu Qatada (may blessings of Allah be upon him) that the Prophet (Sallallahu Alaihi wa Sallam) said: Arafah's fasting removes the sins of two years: the last and the coming year. [Narrated by Muslim , Abu Dawood , aI-Nasa'e and Ibn Maajah ] Also, Ahmed and Ibn Maajah narrated as told by Abu Hurairah (may blessings of Allah be upon him) that The Prophet (Sallallahu Alaihi wa Sallam) has forbidden the fasting of Arafah day or in Arafah (location).
- (Some) days of the month of Muharram, as recorded in Saheeh Muslim and in the Sunan from Hadith Abu Hurairah (may blessings of Allah be upon him) who told that the Prophet (Sallallahu Alaihi wa Sallam) was asked: Which Fast (months to fast) is best after Ramadan? He said: Allah's month Muharram.
- Ashura day, which is the tenth day of the month of Muharram and the ninth day of the same month is added as narrated by Ahmed and Muslim from Ibn Abbas (may blessings of Allah be upon them) who said; When the Prophet fasted Ashura day and instructed others to fast it, they told him that it is a day which is religiously observed by the Jews and the Christians. He said: We will fast the ninth next year. But it did not happen because the Prophet (Sallallahu Alaihi wa Sallam) died. The benefits (Fadhail) of this day are mentioned above in the Hadith of Abu Qatada .
- (Some) days of the month of Sha'ban, as told by Ayisha (may blessings of Allah be upon her), she said: The Prophet (Sallallahu Alaihi wa Sallam) did not fast in any month as much as he did in Shaban. He used to fast (all its days) except few. [Mutafaqun Alayhi]
- Three days of every month, as confirmed in Saheeh Muslim that Abu Hurairah and Abu Zar (may blessings of Allah be upon them) said: The Prophet (Sallallahu Alaihi wa Sallam) advised us never to quit (praying) the two Rak'ah AI-Duha, and the Witr (prayer) before going to bed (at night); and to fast three days of every month. They are preferred to be the thirteenth, fourteenth and fifteenth days (of each month).
- On Mondays and Thursdays as told by Ayisha (may blessings of Allah be upon her) who said: The Prophet (Sallallahu Alaihi wa Sallam) used to (always) fast Mondays and Thursdays ; and the Hadith is written in the Sunan and in others.The preferred days to get fasted are many but it is also good for every Muslim to fast for some preferred days and adhere to it rather than fasting all and then quitting them all. Our Prophet (Sallallahu Alaihi wa Sallam) used to adhere to any deed he commenced as narrated by Muslim .
Answerer: Fatwa center supervised by Dr. Abdullah Al-faqih