A'isha (Allah be pleased with her) reported that a man said to Allah's Apostle ﷺ: My mother died all of a sudden, and I think if she (could have the opportunity) to speak she would have (made a will) regarding Sadaqa'. Will I be entitled to reward if I give charity on her behalf? He (the Holy Prophet) said: Yes.

حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، أَخْبَرَنِي أَبِي، عَنْ عَائِشَةَ، أَنَّ رَجُلاً، قَالَ لِلنَّبِيِّ ﷺ إِنَّ أُمِّيَ افْتُلِتَتْ نَفْسُهَا وَإِنِّي أَظُنُّهَا لَوْ تَكَلَّمَتْ تَصَدَّقَتْ فَلِيَ أَجْرٌ أَنْ أَتَصَدَّقَ عَنْهَا قَالَ
" نَعَمْ " .