Sahih Muslim Book 25, Hadith 18
Allah's Messenger, my mother died all of a sudden without making any will. I think if (she could have the opportunity) to speak she would have made a Sadaqa. Would there be any reward for her if I give charity on her behalf? He (the Holy Prophet) said: Yes.
My mother died all of a sudden, and I think if she (could have the opportunity) to speak she would have (made a will) regarding Sadaqa'. Will I be entitled to reward if I give charity on her behalf? He (the Holy Prophet) said: Yes.
This hadith has been narrated on the authority of Hisham b. 'Urwa with the same chain of transmitters.