Musnad Ahmad 1153:1295

Ibn Numayr narrated to us, Ubaydullah narrated to us, he said: I heard al-Qasim narrating from Aisha, she said: O Messenger of Allah, I do not see Safiyyah as anything but detaining us. He said: "Did she not perform the Ifadah (Tawaf al-Ifadah)?" She said: "Yes." He said: "Then there is no detention upon you." So he departed with her.