What is the ruling on cursing the جدف and saying: "May the جدف be cursed"? And does the matter reach the point of apostasy?

It is not permissible to curse "al-jadf," whether it refers to the grave or to unfermented drinks, especially if it refers to the buried (person). This is because cursing a believer is like killing him, and a believer is not a slanderer nor a curser. Cursers will not be witnesses nor intercessors on the Day of Resurrection. And if a servant curses something, the curse ascends, and if it finds no place, it returns to its speaker if the cursed one is not deserving of it.