A mother vowing to fast if her son survives the operation but without specifying a number of days

Q: We had a diseased child. The doctor decided that he needs surgery in the trachea. His mother made a vow to observe fasting for an unlimited period if he recovers after the surgery. Allah willed that he recovers. However, twenty days after the surgery he had a blockage in his trachea then died. May Allah be merciful with him! What is the ruling on fasting in this case? And how many days should the mother fast?

A: The child's mother has to fulfill her vow because her son recovered after the surgery and his death was accidental. It is sufficient for her to fulfill her vow and fast at least one day because she did not specify a number of days.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.