Or HaChaim on Genesis 49:31/אור החיים על בראשית מ״ט:ל״א

1 שמה קברו את יצחק, there they buried Isaac, etc. Inasmuch as the cave of Machpelah used to belong to Efron the Hittite before Abraham had bought it, the Torah says here: "there they buried Abraham and Sarah." This means that the original owners did no longer use that cave to bury their own dead but that it had become the burial ground for Abraham's heirs, Isaac and Ishmael. When the Torah continues that "there they buried Isaac and Rebeccah," this is a reminder that the cave had become the property of Isaac's heirs Jacob and Esau, excluding Ishmael and his family. When Jacob added that he had buried Leah there, he wanted to exclude Esau's right to be buried there. Sotah 13 quotes Genesis 50,5 which has Joseph telling Pharaoh that Jacob had spoken about the grave he had dug for himself in the land of Canaan as proof for denying Esau a share in that cave.