What is the ruling on taking the remaining marble stones that a brother donated to the mosque, knowing that his initial intention was to give the surplus thereof to his father, and does the ruling differ if the donor informs the officials of this intention or not?

If the donor commanded that the remaining marble be given to his father, they must do so, and there is no legal impediment. The aforementioned verse has no relation to the matter, nor does the Hadith prohibiting revocation of a gift, because the donor did not donate the entire quantity to the mosque, but only what it needed, and commanded that the excess be returned to his father.

If the donor did not command this, and his father asked him, then if the donor confirms it, his father may take it; otherwise not. If it is impossible to ask the donor, his father is required to provide proof.