What is the ruling for a woman whose menstrual period ends at night regarding purification and fasting?

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The ruling for a woman whose menstruation ends during the night is the same as the ruling for a person in a state of Janabah. It is stipulated that her period must cease before the break of dawn; otherwise, if any part of the flow occurs during the day, the fast is invalidated. It is also required that she forms the intention (Niyyah) to fast during the night after her purification begins, as fasting is invalid without a night intention. The evidence supporting this is that since the state of purity is achieved before dawn, delaying the Ghusl until morning does not invalidate the fast, similar to Janabah. Evidence also includes the verse permitting intercourse until the white thread of dawn becomes distinct from the black thread (Quran 2:187), implying that purification follows this period.