Sunan an Nasai
3649
Sahih+2

It was narrated from 'Aishah that a man said to the Messenger of Allah:"My mother died unexpectedly; if she had been able to speak she would have given charity. Should I give charity on her behalf?" The Messenger of Allah said: "Yes." So he gave charity on her behalf

SahihAbu Ghuddah
SahihAl-Albani