It is narrated from Sayyidah Aishah (may Allah be pleased with her) that a man said to the Prophet (peace and blessings be upon him): My mother died suddenly, and I think that if she had had the chance to speak, she would have given charity. If I give charity on her behalf, will there be a reward for her? He (peace and blessings be upon him) said: "Yes."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12630