The age old saying that the apple doesn’t fall far from the tree holds true as we see Isaac introducing Rebekah as his sister to Abimelek.
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.
After experiencing close communion with God (Chapter 18) and seeing the destruction of the twin cities (Chapter 19), one would assume that Abraham would definitely be closer to God than ever before. But he was in fact back to his old ways. Moving to a land without God’s leading, we don’t see him building any altars or even praying to God, giving Sarah to be married to the ruler of that land by letting everyone believe they are siblings again and in the end profiting off of the ruler’s guilt, again!