Musnad Ahmad 1153:1585

Yahya narrated to us, from Ubaydullah, who said: I heard al-Qasim ibn Muhammad say: Aisha said: I said, "O Messenger of Allah, I do not see Safiyyah as anything but one who is detaining us." He said, "And what is her matter?" I said, "She has menstruated." He said, "Did she not perform the Ifadah (Tawaf al-Ifadah)?" I said, "Yes, but she menstruated after that." He said, "Then there is no detention upon you, so depart with her."