The first obvious question that arises in Parshas Chayei Sarah is why do we dedicate so much time to discussing Avraham's purchase of the Maarat HaMachpelah, the Cave of the Forefathers? The funeral of Sarah herself goes all but unmentioned and the funeral of Avraham is a footnote, yet apparently the details of the fairly ordinary bargain is somehow of crucial importance.
Some commentaries tell us that this retelling provides proof of our legal right to the cave, but this seems rather redundant. After all doesn't Rashi already tell us that the reason the entire Torah began with the creation of the world was to tell us that G-d had created all the world and had the right to distribute lands to whom he wanted and therefore had the right to give Israel to the Jewish people. Why then do we need the sale of this particular piece of land, above and beyond G-d giving us the entire land?
And what is the connection between this sale of the land for burying Sarah our Foremother and the marriage of Yitzchak, which comes next? And here another question arises. Hagar and then Keturah (who possibly also was Hagar) was good enough for Avraham himself and Avraham even prayed that her offspring, Yishmael, would walk before G-d and inherit him. And now suddenly Sarah died, Avraham decides to seek a wife for Yitzchak and now the residents of the land are no longer good enough. What changed?
The answer is that what changed is Avraham's experience in burying Sarah. In going to Efron, Avraham came as a Prince of G-d, something they acknowledged. He asked to honestly purchase a piece of property. And yet he was promised it as a gift and then cheated numerous times. This made it all too clear to Avraham who represented the openness of hospitality and generosity, that he could not marry his family into the Caananites. If it was merely a matter of idol worship, that might have been purged. But like the people of Sdom, the Caananites had become debauched by a lack of basic human virtues. Deception and a lack of honesty and generosity had become embedded in them.
Thus Eliezer sets off to find a wife for Yitzchak and the test he uses is premised on generosity and hospitality. The very traits that Efron and Avimelech had demonstrated a lack of. That Hagar had demonstrated a lack of when she abandoned her own child. Thus Avraham had rejected the people of the land for precisely this reason and now sought a member of his family, not simply genetically, but one who shared the traits of his family, the trait that had also saved Lot -- generosity. Thus when Rivka shows generosity and hospitality to Eliezer, this is the sign he needs and he in turn shows generosity toward her... demonstrating himself to be a true servant of Avraham.
The death of Sarah had left a void that Rivka would fill, not merely with her presence, but with her attributes and her actions... continuing the generosity of Avraham's family.
Footnote: I notice the discussion going on in the Torah portion of the Jblogsphere about Rivka's age. Again I'll briefly point out that the chronology that points her as 3 is wrong. Even if we presume that was able to draw the water through a miracle, the attitude of her own family toward her is an excellent demonstration of her actual age.
1. Her family sends her out to draw water. On her own. It's reasonable to assume that neither she nor her family went out expecting a miracle. A 3 year old is simply not even capable of reaching a well, let alone performing the necessary tasks.
2. Her family asks for her opinion on going with Eliezer. It would have been silly for them to ask a 3 year old.
Additionally Rivka is able to alight from a camel. Go look at a 3 year old and find me one who can alight from a camel. On her own. Or even control a camel.
Top that off with the Pasuk telling us two different ways that Rivka is a virgin. An unnecessary point to relate about a 3 year old.
There is no universal view pegging Rivka's age. The evidence in the Pasuk would peg her as a teenager, old enough for her parents to ask about her views, old enough to wear the heavy gold necklaces Eliezer places on her, old enough to manage a camel and alight from one and old enough to wear a veil and use it around men.