Musnad Abu Ya'la al-Mawsili 145:7

Qatan ibn Nusayr al-Ghubari narrated to us, Ja'far narrated to us, Shu'bah ibn al-Habhab narrated to us, from Anas ibn Malik, who said: The Messenger of Allah (may Allah bless him and grant him peace) emancipated Safiyyah and made her emancipation her dowry.