Diana Edelman has a nice article here on Abraham's purchase of the burial cave of Machpelah (Gen 23:3-20). I enjoyed the whole article but liked this last bit the best.
R. Yuden son of R. Simon said: “This is one of three places that the nations of the world cannot charge Israel and say to them ‘this is stolen [land] in your hands.’ They are: the cave of Machpelah, the Temple mount, and the burial plot of Joseph. The cave of Machpelah ‘Abraham paid Ephron’ (Genesis 23:16); the Temple mount ‘David gave Arnon’ (1 Chronicles 21:25), the burial plot of Joseph ‘And he bought the field’ (Genesis 33:19).” [Genesis Rabbah (§79)]
Here the rabbis are picking up on an important theme in this chapter, which emphasizes the legal nature of this purchase. Thus, the long story of Abraham purchasing a burial plot for Sarah from the local Sons of Heth represents the first step towards fulfilling the divine promise.