Bava Batra 159 - A Hard-to-Understand Ruling From Israel

They sent a ruling from Israel: If a son borrowed against his father's property and subsequently died, his son seizes it from purchasers.

Now what is hard to understand here? The son stood to inherit his father. He sold some properties that would be in the future coming to him.  Later he died and thus never inherited those properties. Now his son (a grandson) can tell the buyers, "My father sold you property that he stood to inherit but never inherited, so the sale is void. I inherit it not from my father, but directly from my grandfather." The rule that the grandson in this case inherits directly from the grandfather if derived from " In place of your fathers shall be your sons ..."

So what is difficult? That " In place of your fathers ..." is talking about blessings, not monetary laws.

Art: Arthur Boyd Houghton - Grandfathers Jack in the Box