Is an expiatory offering (kaffarah) for an oath sufficient for not fulfilling a vow to perform the Shafa and Witr prayers, and what is required if the performance was omitted based on the belief that the expiatory offering was sufficient?

First: A vow of obedience must be fulfilled by consensus, based on the Prophet’s (peace be upon him) saying: “Whoever vows to obey Allah, let him obey Him.”

Second: If someone vows an act of obedience and then becomes unable to perform it, they must offer an expiation for breaking an oath (kaffarat yamin), based on his (peace be upon him) saying: “...and whoever vows a vow he cannot fulfill, its expiation is the expiation of an oath.” The vow to pray Shafa' and Witr falls within the scope of one's ability, and it is obligatory to fulfill it. The expiation for an oath that was given is not sufficient, because the vow becomes an obligation that cannot be abandoned without a legitimate Shar'i justification.

Third: As for the days you missed the prayers based on the belief that the expiation for an oath would substitute for the prayer, you are obligated to make them up.