Or HaChaim on Genesis 36:20/אור החיים על בראשית ל״ו:כ׳

1 אלה בני שעיר החודי, These are the sons of Se-ir the Chorite, etc. The reason the Torah writes this whole detailed chapter is only to tell us how generously G'd endowed the wicked Esau on account of the merit of his father and grandfather. Our sages in Shabbat 85 also explain this in the following words of Rabbi Acha bar Yaakov: "The word Chori means that 'freed' the Chorim [the former inhabitants of Se-ir] of their possessions. In other words, the Torah speaks of G'd handing over their lands to the sons of Esau. We have an interesting statement in Sanhedrin 99 saying that Timna who was prince Lotan's sister, the most highly placed woman in that land, became the concubine of Eliphaz, son of Esau because all her efforts to intermarry with either Abraham, Isaac or Jacob were to no avail. Rather than remain a princess in her own right she chose to become a slave in the house of Esau. When her attempt to belong to the Jewish people became frustrated she became the maternal grandmother of Amalek instead.