This passage explains why Scripture does not enumerate the sons of Esau until after the death of Isaac, while Jacob's sons are enumerated long before he dies. This, we learn, is because Esau abandoned the true Faith completely, leaving Jacob with an enhanced portion, as well as the heritage of his father and his ancestors.
Isaac, his son Jacob, and their succeeding generations, forged the spiritual path that led to the revelation of the Torah, and therefore, they represent its eternal, supernal Light. Esau, however, embodies the force of darkness and eternal death. This section connects us to Light of the Torah, expressed through the Patriarchs Isaac and Jacob.