I vowed to fast every Monday and Thursday in Sha'ban; what is the ruling if she menstruates or if it is the day of doubt?

The questioner : A woman vowed to fast on Thursdays and Mondays in Sha'ban for the rest of her life. If she breaks her fast due to menstruation or post-natal bleeding, does she have to make up the fasts? And if the last of these days is the day of doubt, the last day of Sha'ban, what is obligatory for her?

The Shaykh : First, we must know the reason for the vow. Is it a vow of voluntary worship, meaning it is an absolute vow, or is it a vow conditional on something? We will answer in detail what does not contradict...

The questioner : Please, Shaykh.

The Shaykh : If it is conditional on something, such that she said, "If I do such-and-such, then I have a vow to Allah to fast on Mondays and Thursdays in Sha'ban," and her intention with this is to prevent herself from the act, then this vow of hers is in the ruling of a trust. If she wishes, she expiates with the expiation for an oath and is absolved of the vow; if she wishes, she fasts the vow. As for if this is an absolute vow, because her vow is to fast for Allah on Mondays and Thursdays in Sha'ban, then she is required to fulfill what she vowed, because fasting on Mondays and Thursdays is obedience to Allah the Exalted and Majestic. It is established from the Prophet (peace and blessings be upon him) that he said . If a day of menstruation coincides, she makes it up. Then, is an expiation obligatory for her or not? I mean, is the expiation for an oath obligatory for her or not? The correct view is that it is not obligatory for her, Shaykh, if a day of menstruation coincides. And what about the day of doubt, Shaykh? Yes, O mother of Hay. Yes, please. She makes it up, and the correct view is that the expiation for an oath is obligatory for her because she delayed it without her choice.
And if the day of doubt coincides, as in this year where Thursday was the thirtieth day of Sha'ban, then she fasts it and there is no harm. This woman fasted on Thursday. Not because it was the day of doubt, but because it was the day she vowed to fast.