Sahih al-Bukhari, Book 23, Hadith 141 (In-Book) ⓘ

Narrated Aisha: A man said to the Prophet (p.b.u.h), "My mother died suddenly and I thought that if she had lived she would have given alms. So, if I give alms now on her behalf, will she get the reward?" The Prophet replied in the affirmative.

حَدَّثَنَا سَعِيدُ بْنُ أَبِي مَرْيَمَ، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، قَالَ أَخْبَرَنِي هِشَامٌ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ‏.‏ أَنَّ رَجُلاً، قَالَ لِلنَّبِيِّ صلى الله عليه وسلم إِنَّ أُمِّي افْتُلِتَتْ نَفْسُهَا، وَأَظُنُّهَا لَوْ تَكَلَّمَتْ تَصَدَّقَتْ، فَهَلْ لَهَا أَجْرٌ إِنْ تَصَدَّقْتُ عَنْهَا قَالَ ‏ "‏ نَعَمْ ‏" ‏‏.‏