Sahih Al Bukhari – Book of Wills And Testaments (Wasaayaa)

Volumn 004, Book 051, Hadith Number 023.
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Narated By Ibn ‘Abbas Radi-Allahu ‘anhu : Sad bin Ubada Radi-Allahu ‘anhu consulted Allah’s Apostle

Sallallahu ‘Alaihi Wa Sallam saying, “My mother died and she had an unfulfilled vow.” The Prophet PBUH said, “Fulfill it on her behalf.”