It is narrated from Sayyiduna Sahl bin Hunayf (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) took Sayyidah Safiyyah bint Huyayy (may Allah be pleased with her), who was from Banu al-Nadir, captive, and she was among the wealth that Allah Almighty granted him (peace and blessings be upon him) as fay' (spoils gained without fighting).
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20545