Shaykh Abdul Azeez ibn Baaz rahimahullaah in his Majmoo` Fataawaa vol. 13 pg. 251 was asked the following question:
Q: What is the evidence for specifying the deceased benefiting from some actions and not others?
A: These affairs are tawqeefeeyah (depend upon textual evidence from Allaah or His Messenger, from the Quraan or the Sunnah only), and there is no room for opinion in such affairs, rather one acts in accordance to what the proofs indicate due to the generality of his sallAllaahu alaihi wa sallam saying: “Whoever invents into this affair of ours that which is not from it then it will be rejected.” Agreed upon its authenticity. (Bukhaaree and Muslim)