Answered by Shaykh Faraz Rabbani
What should a woman do if she started her menstruation whilst she was performing her salah?
Walaikum assalam wa rahmatullah,
In the Name of Allah, Most Merciful and Compassionate
Her state of ritual purity is lifted when her menstruation begins. Given that ritual purity is a condition for the validity of her prayer, her prayer itself would be immediately invalidated. However, she would have the full reward for the prayer, because “Actions are by intentions, and each person shall have what they intended,” as the Beloved Messenger of Allah (peace and blessings be upon him) told us.
It is recommended during one’s period to sit during each of the prayer times and to perform some remembrance of Allah–the benefits of doing so are clear to those who reflect.
And Allah alone gives success.
Wassalam,
Faraz Rabbani