Short answer
The fast of Dawud (Prophet David) is fasting one day and leaving the next, all year. The Prophet ﷺ called it the most beloved fast to Allah and the most anyone should do. In the Hanafi school it is the best voluntary fast. Fasting every single day without a break is makruh.
Fasting alternate days is the best of voluntary fasts. Fasting continuously every day (sawm al-dahr) is makruh, because it weakens a person and becomes a habit rather than worship; if it includes the two Eids and the days of tashriq it is makruh tahrimi.
Other madhhabs
- Shafi'i
- Fasting every day apart from the forbidden days is not disliked for someone it does not harm and who does not neglect any right; otherwise it is disliked.
Explanation
Abdullah ibn Amr ibn al-As was a young Companion who fasted every day and prayed all night. When this reached the Prophet ﷺ, he told him to fast and also eat, pray and also sleep, because his eyes, his body and his family had a right over him. Abdullah said he could manage more, so he was told to fast the fast of Dawud: one day on, one day off. When Abdullah asked for more still, he said no fast is better than that.
How to keep it:
- Fast one day, eat the next, and repeat.
- Skip the forbidden days (the two Eids and the three days after Eid al-Adha), then carry on.
- If the pattern puts a fast on a Friday alone, that is fine, because you did not choose Friday for itself.
- A wife keeps it with her husband's agreement. See a wife's voluntary fast.
Is it for everyone? It is the most a person should aim for, not a duty. The Prophet ﷺ also taught that three days a month equals fasting a whole lifetime in reward, since each good deed counts ten times. If alternate days would harm your work, health or family, three days a month, or Mondays and Thursdays, is the better sunnah for you.
Fasting every day. The Prophet ﷺ said: whoever fasts forever has not fasted. The Hanafi scholars therefore class nonstop fasting as makruh. See the sunnah fasts and Mondays, Thursdays and the white days.
The evidence
Sahih al-Bukhari 1131
Sahih... وأحب الصيام إلى الله صيام داود ...
"The most beloved fasting to Allah is the fasting of Dawud: he would fast a day and leave a day."
Alternate days is the best voluntary fast.
Sahih al-Bukhari 1977
Sahih... فصم وأفطر وقم ونم فإن لعينك عليك حظا ...
"Fast and eat, pray and sleep, for your eye has a right over you."
Voluntary fasting must leave room for the body's and family's rights.
Sahih al-Bukhari 1975
Sahih... صيام ثلاثة أيام من كل شهر صيام الدهر كله ...
"Fasting three days of every month is like fasting the whole year."
A lighter sunnah for those who cannot keep alternate days.
Where the ruling is recorded
- al-Fatawa al-Hindiyya, Kitab al-Sawm, chapter on what is desirable and disliked in fasting. The fast of Dawud is the best voluntary fast; continuous fasting is disliked.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Sawm, before the chapter on what breaks the fast. Sawm al-dahr is makruh, and fasting the days of Eid and tashriq is makruh tahrimi.
- al-Majmu' (Nawawi), Kitab al-Siyam, chapter on voluntary fasting. The Shafi'i view on fasting every day apart from the forbidden days.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. 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.