Sahih Bukhari
Wills and Testaments (Wasaayaa)
Volume: 004 / Book Number: 051 / Hadith Number: 22
Narrated 'Aisha:
A man said to the Prophet, "My mother died suddenly, and I think that if she could speak, she would have given in charity. May I give in charity on her behalf?" He said, "Yes! Give in charity on her behalf."