Genesis 34-38
One must question why the book does not end at Genesis 36, for if Abraham is to have seed, that of a nation of 12 tribes, then the 12 sons are now fully represented and thus complete. Yet it is not physical representation that is needed. It is a regard for God and the promise of the Seed of the Woman to deliver them, which they are to give to the Gentiles. Reuben committed incest with a covenant mother. Simeon and Levi treated the covenant sign of circumcision as common, using it as a trick for vengeance.
Thus the story must continue for the sons must come to completion, that is, they need to regard the covenant promise to Abraham through trust in the Seed. That has not happened and must happen for Israel to be the nation who is able to bless the Gentiles with the message of that promise (and ultimately for the One to come through them). It is important to say that again. Israel is the nation that was meant to carry the message of Messiah to the nations. But the 12 sons had rejected it and were, in fact, blasphemous toward the covenant. So the Abrahamic Covenant cannot be complete until Israel comes to realize their Messiah.
Dr. Charles Baylis
Video
Chapters 34-36
Chapters 37-38
Audio
Commentary
Links & Sources
TeachMeTheBible.com - Dr. David Klingler
The Spring Church Sermons - Prof Caleb Foley
Traceway Church Sermons - Dr. Nathan Tullos
TheBiblicalStory.org - Dr. Charles Baylis