Reference: al-Muntaqaa min Fataawa Shaykh Saalih al-Fowzaan – Volume 2, Page 161, Fatwa No.139
Question: What are the things which benefit the deceased by way of the living? And is there a difference between physical and non-physical acts of worship? We hope you will clarify these issues for us, and outline a rule which we could refer to whenever we come across issues such as these; [Please] provide us with a fatwa, and may Allaah grant you blessings [in your affairs]?
Response: The deceased benefits from the action(s) of the living by way of that which [authentic] evidence indicates [permissibility] – from supplication [for the deceased], and the seeking of forgiveness for him (the deceased) and giving in charity on his (the deceased’s) behalf and [performing] the Hajj and the ‘Umrah on his behalf and paying off his debts and executing his Islaamic will; All of these have been legislated for. And some of the scholars have attached to this all acts of worship which a Muslim does deeming their reward for a[nother] Muslim who is alive or dead. However, that which is correct is to limit [oneself] to that which [authentic] evidence indicates [permissibility] as this will be in accordance with His (Subhaanahu wa Ta’aala) saying:
…and Allaah is the most knowledgeable [of all affairs].