Short answer
Yes. Fasting on Mondays and Thursdays, and on the three white days (the 13th, 14th and 15th of each Islamic month), are well-established sunnah fasts. They are mustahabb (recommended) in the Hanafi school and in all four schools. Three days a month carry the reward of fasting the whole month.
Fasting Mondays and Thursdays is mustahabb, and so is fasting three days each month, best on the 13th, 14th and 15th of the lunar month. The intention for these voluntary fasts may be made before midday if you have not eaten.
Other madhhabs
- Maliki
- Fasting three days a month is recommended, but Imam Malik disliked fixing them on the white days in particular, so that people would not think them obligatory.
Explanation
Mondays and Thursdays. The Prophet ﷺ said that deeds are presented to Allah on Mondays and Thursdays, and he loved for his deeds to be presented while he was fasting. Asked about fasting on Monday, he said it was the day he was born and the day revelation first came to him.
The white days. These are called white because the moon is full and the nights are bright. The Prophet ﷺ told Abu Dharr that if he fasted three days of a month, he should fast the 13th, 14th and 15th. Abu Hurayra said his close friend advised him to fast three days every month. Since each good deed is multiplied tenfold, three days a month is like fasting the whole month.
- If you miss the white days, fasting any three days of the month still earns the sunnah of three days.
- You can make the intention in the morning, before midday, if you have not eaten.
- If you owe qada, you may fast it on a Monday or Thursday; it counts as your qada.
The four schools agree that these fasts are recommended, with the small Maliki note above. For other sunnah fasts, see the Day of Arafah, Ashura and the six days of Shawwal.
The evidence
Jami' at-Tirmidhi 747
Graded sahih... تعرض الأعمال يوم الاثنين والخميس فأحب أن يعرض عملي وأنا صائم ...
"Deeds are presented on Monday and Thursday, and I love that my deeds are presented while I am fasting."
The reason for the sunnah of fasting these two days.
Sahih Muslim 1162
Sahih... ذاك يوم ولدت فيه ويوم بعثت ...
"That is the day I was born, and the day I was sent as a prophet."
His answer when asked about fasting on Mondays.
Jami' at-Tirmidhi 761
Graded hasan sahih... إذا صمت من الشهر ثلاثة أيام فصم ثلاث عشرة وأربع عشرة وخمس عشرة ...
"If you fast three days of the month, fast the thirteenth, fourteenth and fifteenth."
The basis for fasting the white days.
Sahih al-Bukhari 1981
Sahih... صيام ثلاثة أيام من كل شهر وركعتي الضحى ...
"Abu Hurayra said he was advised to fast three days of every month and pray two rakat of Duha."
Fasting three days a month is a steady sunnah.
Where the ruling is recorded
- al-Durr al-Mukhtar, Kitab al-Sawm, section on the kinds of fasts. Fasting Mondays and Thursdays and the white days is among the recommended fasts.
- Nur al-Idah with Maraqi al-Falah, Kitab al-Sawm, section on the kinds of fasts. Three days of every month, preferably the white days, are recommended.
- Mukhtasar Khalil with al-Sharh al-Kabir, Bab al-Siyam, recommended fasts. The Maliki dislike of fixing the white days.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.