Is it permissible for a son to own land that his father relinquished to him before his death, with a document and two witnesses, or must it be divided among the heirs?

If the son did not fully take possession of the gifted plot during his father's lifetime, then the gift is invalid, and the plot is considered an inheritance to be divided among all heirs, based on the hadith of Abu Bakr to his daughter Aisha, may Allah be pleased with them both. Real estate registration is not a condition for the validity of a gift but rather for documentation. Equality among children in gifting is obligatory; otherwise, it is void. The son must return the gift for it to be divided with the estate if his siblings do not agree to his sole possession of it.