the lawful pastimes, and they are days of remembering Allah: during them it is prescribed to pronounce the takbīr. They are the “appointed days” of which Allah, Exalted is He, says, “And remember Allah during the appointed days” (al-Baqarah 2:203). They were named the Days of Tashrīq because people used to cut the meat of their pilgrimage and festival sacrifices into strips and expose it to the sun so that it would dry and could be stored for several days.

2 – Because of these religious duties and the need to gain strength to perform them, and because Muslims, coming straight after the joy of the festival, eat from what they have offered to Allah of hady and other sacrifices—and are therefore in the hospitality of Allah—fasting on these days has been forbidden. No fast performed on them is valid, whether obligatory, supererogatory, vowed, or of any other category; should anyone fast for any such purpose, it will not count, for it has not been observed in its proper time and is therefore invalid.

Scholarly disagreement
The jurists differed regarding fasting on the Days of Tashrīq and produced three opinions:

1. It is invalid to fast them except for the compensatory fast required of someone performing tamattuʿ or qirān who cannot obtain a sacrificial animal.
2. Fasting on them is invalid absolutely—neither for tamattuʿ, nor qirān, nor anything else.
3. It is permissible to fast them for tamattuʿ or qirān and for any fast that has a specific cause, such as a vow or an expiation, but not for a fast without a cause; such a fast would be invalid.

The strongest of these views is that fasting on those days is prohibited and invalid, except for a pilgrim performing tamattuʿ or qirān who lacks a sacrificial animal; in that case he may fast the three Days of Tashrīq, in accordance with the hadith under discussion.

Al-Nawawī said, “The position best supported by the evidence is that such a fast is valid and permissible for a pilgrim performing tamattuʿ, because the hadith that grants him this concession is authentic and explicit; there is therefore no reason to depart from it.”