Riyad as-Salihin 948
'Aishah (May Allah be pleased with her) reported:
A man said to the Prophet (ﷺ): "My mother has died suddenly. I think that if she were able to talk (alive) she would have given in Sadaqah (charity). So, if I give Sadaqah now on her behalf, will she get the reward?" The Messenger of Allah (ﷺ) said, "Yes (she will be rewarded for that)." [Al-Bukhari and Muslim] .
وعن عائشة رضي الله عنها أن رجلاً قال للنبي صلى  الله عليه وسلم ‏:‏ إن أمي افتلتت نفسها وأراها لو تكلمت، تصدقت، فهل لها أجر إن تصدقت عنها‏؟‏ قال‏:‏ ‏
"‏نعم‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏