Reference: Fataawa Noor ‘alad-Darb – Question No.6451, Pages 277-278, Volume 12
Question: [Please] guide me to good deeds which I can do so [their reward] reach my father, and may you be rewarded.
Response: [Regarding those] good deeds whose reward can reach your father, [then] the best of them, and the most beneficial are what the Prophet ﷺ has instructed [us with], as he said:
So supplicating is the best [deed] which a person can gift his deceased father and mother, or relative or friend, and because of this the Prophet ﷺ did not say that a person should do [any specific] deed on behalf of the deceased, rather he said:
So that which is befitting for us is to increase in supplicating for those of our deceased, and render our righteous deeds for ourselves, for indeed we will be in need of these deeds, just as the deceased will be in need of them.