Sahih Muslim 1004aBook 12, Hadith 63
وَحَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا مُحَمَّدُ بْنُ بِشْرٍ، حَدَّثَنَا هِشَامٌ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، أَنَّ رَجُلاً، أَتَى النَّبِيَّ صلى الله عليه وسلم فَقَالَ يَا رَسُولَ اللَّهِ إِنَّ أُمِّيَ افْتُلِتَتْ نَفْسَهَا وَلَمْ تُوصِ وَأَظُنُّهَا لَوْ تَكَلَّمَتْ تَصَدَّقَتْ أَفَلَهَا أَجْرٌ إِنْ تَصَدَّقْتُ عَنْهَا قَالَ " نَعَمْ " .
My mother died suddenly without having made any will. I think she would have definitely given Sadaqa if she had been able to speak. Would she have a reward if I gave Sadaqa on her behalf? He (the Holy Prophet) said: Yes.