Permissibility of fasting on a day other than the vowed Thursdays all his life

A: The basic ruling is that it is obligatory to fulfill vows of obedience. The Prophet (peace be upon him) said, “Anyone who vows to obey Allah, should obey Him.” As the condition you made for the vow was realized, it is obligatory on you to fast every Thursday as long as you are able to do so and nothing prevents you from it, such as illness or old age. You can make up for the days of Sawm that you broke in the past with other days, but you cannot substitute another day for the Thursday that you vowed to fast. Also, you do not have to obey your father to break your vow, because breaking a vow of obedience is a sin and there is no obedience to a creature in disobedience to the Creator. In the future you should avoid making vows, because they do not bring good, as the Prophet (peace be upon him) said, “Avoid making a vow, as it does not bring good, but is a means of extracting from the miserly.” We ask Allah to help you perform your obligation patiently, with the hope of reward from Allah.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.