It was narrated from Aishah that a man came to the Prophet (ﷺ) and said:
"My mother died unexpectedly and she had not made a will. I think that if she could have spoken, she would have given in charity. Will she have a reward if I give in charity on her behalf, and will I have a reward?" He said: "Yes."
English reference: Vol. 3, Book 22, Hadith 2717
Arabic reference: Book 22, Hadith 2821