Musannaf Ibn Abi Shayba 25:14

Ibn Abi Ghunyah narrated to us, from his father, from al-Hakam, who said: If a man makes a will and exceeds the third, and he seeks permission from his son during his lifetime, and he (the son) grants him permission, then when he (the father) dies, it returns to his son: if he wishes, he may authorize it, and if he wishes, he may reject it.