Is what the man wrote for his nephews considered permissible or forbidden, knowing that what he wrote were official contracts for most of his property, and not a will, and this man has passed away?

A man's written declaration bequeathing his money to his nephews is void unless he delivers what he gifted to them during his lifetime, while he is of sound mind and capable of disposing of his property, and they take legal possession of it. If he dies before this possession occurs, then what he wrote becomes an inheritance to be divided among all his heirs according to their prescribed legal shares.