Yahya related to me from Malik from Ibn Shihab from Ubaydullahibn Abdullah ibn Utba ibn Masud from Abdullah ibn Abbas that Sad ibnUbada questioned the Messenger of Allah, may Allah bless him and granthim peace, and said,"My mother died while she still had a vow whichshe had not fulfilled." The Messenger of Allah, may Allah bless himand grant him peace, said, "Fulfill it for her."
USC-MSA web (English) reference: Book 22, Hadith 1
Arabic reference: Book 22, Hadith 1012