What is our duty regarding our inherited land, as it is said that our great-great-grandfather wronged his three daughters and deprived them of their inheritance, knowing that these are mere rumors and the daughters are deceased, and what is the ruling on the gift I received from this land from my father?

You are not required to do anything regarding your share of the land unless you are certain that your grandfather wronged his daughters, because certainty is not removed by doubt. Even if you confirm his wrongdoing, most scholars have held that a gift becomes valid for the one it was given to if the giver dies before making an amendment; therefore, you are not obliged to do anything.

However, according to the other view, if you can reach the daughters' heirs and give them their rights or seek their forgiveness, then do so. Otherwise, take out the percentage of their rightful share from the land or its value and give it as charity for good causes.