Related for Avodah Zarah 73:18

"One who writes his property to his son, he needs to write for him "From today and after my death"—words of Rabbi Yehudah." Rabbi Yoseh says: "He does not need to since the date in the contract proves it for him." Rabbi Yehudah said to him: "But doesn't the date in the contract only prove from the moment that it was written? One who writes his property to his son and returns and acquires different property, anything that wasn't included in the original gift—this now belongs to the inheritors [and follows the normal rules of inheritance, equal shares to everyone except a double portion for the firstborn, and overrides the gift]."