Giving charity on behalf of a deceased mother

A man said to the Prophet ﷺ, “My mother died suddenly, and I think that if she had been able to speak, she would have given charity. Will she have a reward if I give charity on her behalf?” He said: "Yes."

أَنَّ رَجُلاً قَالَ لِلنَّبِيِّ ﷺ: إِنَّ أُمِّي افْتُلِتَتْ نَفْسُهَا، وَأَظُنُّهَا لَوْ تَكَلَّمَتْ تَصَدَّقَتْ، فَهَلْ لَهَا أَجْرٌ إِنْ تَصَدَّقْتُ عَنْهَا؟ قَالَ: «نَعَمْ».