Sunnah.com reference : Book 7, Hadith 224English translation : Book 7, Hadith 967Arabic reference : Book 7, Hadith 960
Narrated 'Aishah (RA):
A man came to the Prophet (ﷺ) and said, "O Allah's Messenger, my mother had died suddenly, and did not make a will. And I think she would have given out Sadaqah if she had been able to speak, so will she get a reward if I gave out Sadaqah on her behalf?" He replied, "Yes."

[Agreed upon; the wording is Muslim's].
وَعَنْ عَائِشَةَ ‏-رَضِيَ اَللَّهُ عَنْهَا‏- { أَنَّ رَجُلاً أَتَى اَلنَّبِيَّ ‏- صلى الله عليه وسلم ‏-قَالَ: يَا رَسُولَ اَللَّهِ ! إِنَّ أُمِّي اُفْتُلِتَتْ نَفْسُهَا وَلَمْ تُوصِ , وَأَظُنُّهَا لَوْ تَكَلَّمَتْ تَصَدَّقَتْ , أَفَلَهَا أَجْرٌ إِنْ تَصَدَّقْتُ عَنْهَا ? قَالَ : " نَعَمْ }  مُتَّفَقٌ عَلَيْهِ , وَاللَّفْظُ لِمُسْلِمٍ  1‏ .‏‏1 ‏- صحيح .‏ رواه البخاري ( 1388 )‏ ، ومسلم ( 1004 )‏ .‏ وزاد البخاري في رواية ( 2960 : " تصدق عنها ".‏