Where does a woman whose husband has died observe her waiting period?

Question:
Honorable Shaykh, may Allah grant you success. This questioner says: My father passed away, and he had another wife besides my mother. This wife’s identity is unknown, and I am afraid of the responsibility. Should I let her go with her brothers to observe the waiting period for widowhood with them? Or is it obligatory for me to keep her in a room in my house?

Answer:
Yes, she observes the waiting period in the husband’s house where she is. Once the waiting period is completed, she may go wherever she wishes, because remaining in the marital home during the waiting period is one of the obligations of the waiting period.