If a person vows to fast on a specific day every week, such as Friday, in the event that Eid al-Fiṭr or Eid al-Aḍḥā[6] falls on a Friday, or if on Friday the person has another legitimate excuse to not fast, such as travelling or ḥayḍ, he/she must not fast on that day but must keep a qaḍāʾ fast.