Is it permissible for me to give charity and dedicate its reward to my parents who have passed away? What is the virtue of doing so?

The obligation to be kind and dutiful toward one’s parents is mentioned in many places in the Quran; Allah Almighty says “And your Lord has decreed that you worship none but Him, and that you show kindness to parents. Whether one or both of them attain old age in your life, do not say to them a word of disrespect, nor repel them, but address them in terms of honor. And lower to them the wing of humility out of mercy, and say, ‘My Lord, have mercy upon them as they raised me when I was small’” (Quran, 17:23–24). This and other Quranic injunctions are not limited by circumstances or time. Accordingly, one must honor one’s parents during their lifetime, and if that was overlooked, one should honor them after they have passed away.

Abu Usayd Malik Ibn Rabiʿa al-Saʿidi (may Allah be pleased with him) said, “While we were in the company of the Messenger of Allah (peace and blessings be upon him), a man from the tribe of Bani Salamah came and said, ‘O Messenger of Allah, is there any way I can continue to honor my parents after they have passed away?’ He said, ‘Yes, by praying for them, seeking forgiveness for them, fulfilling their promises after their passing, maintaining ties of kinship which cannot be maintained except through them, and honoring their friends’” (Abu Dawud).

An additional way to honor one’s parents after their passing is to give charity and dedicate its reward to them, especially ongoing charity whose benefits continue to reach them. ʿAbdullah Ibn ʿAbbas (may Allah be pleased with them both) narrated that a man told the Prophet (peace and blessings be upon him), “My mother has passed away; will it benefit her if I give charity on her behalf?” The Prophet (peace and blessings be upon him) replied, “Yes.” The man then said, “I have an orchard, and I ask you to bear witness that I have given it in charity on her behalf’” (recorded by al-Bukhari in his Sahih).

ʿAʾisha (may Allah be pleased with her) narrated that a man told the Prophet (peace and blessings be upon him), ‘My mother passed away suddenly without leaving a will. I think that if she could speak, she would have given charity. If I give charity on her behalf, will she receive the reward, and will I earn a reward as well?’ The Prophet (peace and blessings be upon him) replied, ‘Yes’” (recorded by Muslim in his Sahih). Abu Huraira (may Allah be pleased with him) narrated that a man told the Prophet (peace and blessings be upon him), “My father passed away. He left behind property without making a will regarding it. Would giving charity on his behalf earn him [Allah’s] forgiveness?” He replied, “Yes” (Muslim).

Another way to show dutifulness to one’s deceased parents is to perform any unfulfilled vows of fasting or expiatory fasts on their behalf.
ʿAʾisha (may Allah be pleased with her) narrated that the Messenger of Allah (peace and blessings be upon him) said, “Whoever passes away having missed fasts, their guardian should fast on their behalf” (Bukhari and Muslim).

Giving charity and dedicating its reward to one’s deceased parents is a legitimate and meritorious act, and its reward reaches them by Allah’s permission.

And Allah the Almighty knows best.