Vowing to fast a day every month if she leaves the hospital in good health

Q: A woman had a car accident and was admitted to hospital. She made a vow that if she recovers and leaves hospital, she will observe Sawm (fasting) one day every month. Now she is having a hard time observing Sawm, especially on very hot days. Please advise.

A: A vow to do an act of obedience should be fulfilled. It was authentically reported from the Prophet (peace be upon him) that he said, A person who vows to do an act of obedience to Allah should do so. She has to observe Sawm one day of every (Part No. 23; Page No. 281) month as long as she is able to do so.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.