Vowing to fast on Mondays and Thursdays until his death

Q: I am a feeble woman. One of my children is mentally ill. As I like to observe Sawm (Fast), I have made a vow to observe Sawm on Mondays and Thursdays as long as I live. In view of my inability to continue doing this because I have to care for my children, especially the sick one, I have become confused. As a result, I want to ask whether or not I can give Sadaqah (voluntary charity) instead of observing Sawm. Please answer me. May Allah guide you to that which is good!

A: If the reality is as you mentioned that you are unable to observe Sawm due to your feebleness, it is permissible for you to offer Kaffarah (expiation) for an oath. The Kaffarah involves feeding ten Miskins (needy persons) the average meal that one feeds their family, or providing them with clothing by giving each one a piece of cloth that is enough to cover their `Awrah (parts of the body that must be covered in public), or emancipating a believing slave. If none of these is affordable, you must observe Sawm for three consecutive days.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.