Responsa for Bava Batra 317:1

איתמר בן שמכר בנכסי אביו בחיי אביו ומת בנו מוציא מיד הלקוחות וזו היא שקשה בדיני ממונות ולימרו ליה אבוך מזבין ואת מפיק

it [must] have been made: [If] a son sold the estate<span class="x" onmousemove="('comment',' His share of the inheritance. ');">¹</span> of his father, during the lifetime of the father,<span class="x" onmousemove="('comment',' I.e., while it was still in his father's possession. ');">²</span> and he died, his son<span class="x" onmousemove="('comment',' The son of the dead man who sold his share in his father's estate. ');">³</span> may take [it] away from the buyers;<span class="x" onmousemove="('comment',' That which his father had sold them. That sale was invalid because his father's father having been alive at the time, his father was not yet in possession of the land he sold; and, since he died before his father, the land has never come into his possession. Hence the son (the grandson of the owner) inherits that land from his grandfather and is entitled therefore, to take it away from the buyers, on his grandfather's death. ');">⁴</span>

Teshuvot Maharam

Teshuvot Maharam