Is the husband entitled to know the type of his wife's fasting, whether it is voluntary or a vow, and what is the reason for the vow?

A woman is not permitted to observe a voluntary fast except with the permission of her present husband. He has the right to prevent her from it through intercourse if she fasts without his permission. As for an obligatory fast, such as making up for Ramadan (definition) when time is short, she does not need his permission and he does not have the right to prevent her. Scholars have attached to voluntary fasting all self-imposed obligations by the woman, such as vows or expiations, if they do not have a specific time and there is a fear of them expiring. The husband has the right to know the type and reason for his wife's fasting, and it is recommended for him not to prevent her from a fast that does not harm him.