What is the ruling on opening the grave of the first deceased female and placing sand over her body to bury a second deceased female in the same grave, and is expiation due upon the one who does so?

It is not permissible to exhume a grave and bury someone other than its occupant in it, because the burial place of a Muslim is designated for them as long as any part of them remains. Exhumation is only permissible for a valid reason, such as recovering money, or fearing for the deceased from predators or floods. Whoever committed this act must repent, seek forgiveness, feel remorse, seek forgiveness for the mother, and supplicate for her with mercy and forgiveness.