Rebecca replaces Sarah as the leading lady of this story and we see God leading this family even while they are making seemingly arbitrary choices, regarding a burial site and perhaps a not so arbitrary choice in finding a life partner for Isaac.
Abraham saw a ram caught in a thicket and that ram replaced his son as the burnt offering. Just like that ram replaced Isaac on the alter, Jesus replaced all of us when he died for our transgressions. Perhaps this was the symbolic gesture that God was giving us through this example of a father sacrificing his son.
We saw in the last chapter that God had enabled everyone in Abimelek’s household to conceive again but Sarah was still kept barren. Abraham had laughed at the very thought of Isaac being born to Sarah, Sarah now has joyous laughter that God came through for her despite her disbelief and then there is Ishmael who is mocking his new younger brother. The Hebrew texts quite aptly say that Ishmael was laughing at Isaac. That captures the sentiment of everyone involved in this saga.