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

Volumn 004, Book 051, Hadith Number 019. 
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Narated By Ibn 'Abbas

Razi Allah Anhu

 : The mother of Sad bin 'Ubada RA died in his absence. He said, "O Allah's Apostle

Peace Be Upon Him

! My mother died in my absence; will it be of any benefit for her if I give Sadaqa on her behalf?" The Prophet said, "Yes," Sad said, "I make you a witness that I gave my garden called Al Makhraf in charity on her behalf."