Musnad Abu Ya'la al-Mawsili 111:71

Abdullah ibn Umar ibn Aban narrated to us, Abduh ibn Sulayman narrated to us, from Hisham ibn Urwah, from Bakr ibn Wa’il, from al-Zuhri, from Ubaydullah ibn Abdullah, from Ibn Abbas, who said: Sa’d ibn Ubadah came to the Prophet, peace and blessings of Allah be upon him, and said: "My mother has died, and she had a vow upon her which she did not fulfill." The Prophet, peace and blessings of Allah be upon him, said to him: "Fulfill it on her behalf."