What are the hadiths and situations that prevent an heir from revoking a gift made by their testator?

If an heir willingly relinquishes their share of an inheritance, and they are of sound mind and adult, and the relinquished share has been taken possession of by the one it was given to, then this is considered a complete gift from which there is no turning back. This is based on the saying of the Prophet, peace and blessings be upon him: "The one who takes back his gift is like the one who takes back his vomit." However, if the gift was not completed according to its conditions, then he may retract it, for a gift is not complete until possession is taken. An example of this is the stance of Abu Bakr Al-Siddiq regarding his gift to his daughter Aisha, may Allah be pleased with them both.