How do we reconcile the permissibility of dedicating the reward of good deeds to the deceased with Allah Almighty's saying: "Whoever does righteousness, it is for his [own] soul" and "If you do good, you do good for yourselves"? And do these verses mean that a person's reward is only for himself and cannot be dedicated to others?

Clarification on the validity of dedicating the reward of good deeds in principle, and the disagreement concerning the specific types of acts of obedience whose reward reaches others. Verses such as: ﴿Whoever does righteousness, it is for his [own] soul; and whoever does evil, it is against it﴾ (Al-Jathiyah/15), do not negate the validity of dedicating the reward of acts of obedience. These verses explain that the benefit of good deeds accrues to their doer, and they have no relation to the issue of the benefit of deeds reaching others. So, whoever responds and obeys will receive the full reward, as in His (Allah's) saying: ﴿Whoever does righteousness, it is for his [own] soul; and whoever does evil, it is against it. And never is your Lord unjust to [His] servants﴾ (Fussilat/46).

And if these verses are silent about the benefit of deeds reaching others, other texts have clarified that a believer may benefit others through some of his deeds, such as supplication, calling to goodness, and enjoining what is right, as stated in Prophetic hadiths like: "Whoever guides to a good deed will have a reward like that of its doer" (Narrated by Muslim (1893)).

And a servant's benefiting others through some good deeds is itself a good deed, so it falls under the generality of the verses mentioned, such as His (Allah's) saying: ﴿Whoever does righteousness, it is for his [own] soul﴾.