Vowing to fast but being unable

A: 1. Whoever makes a vow of disobedience, is not permitted to fulfill such a vow. They have to offer a Kaffarah for a broken oath, as the Prophet (peace be upon him) said, No vow must be taken to do an act of disobedience, and the atonement for it is the same as for an oath. (Related by Ahl-ul-Sunan (authors of Hadith compilations classified by jurisprudential themes) 2. Whoever makes a vow of obedience and is unable to fulfill it out of elderliness or an incurable disease, or for other reasons, has to offer a Kaffarah for a broken oath to absolve themselves from such a vow. (Part No. 23; Page No. 338) This is because Ibn `Abbas (may Allah be pleased with them) said, If anyone takes a vow but can not fulfill it, its atonement is the same as that for a broken oath. (Related by Abu Dawud, who said that the person who reported such a saying attributed it to Ibn `Abbas.) 3. Whoever delays the vow to do something good, has to make up for it and they do not need to offer a Kaffarah. This is similar to a person who breaks Sawm in Ramadan and then makes up for it. Such a person need not offer a Kaffarah. Allah knows best!May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.