The Reason For Egypt

This is another one of those very difficult passages in Genesis. Why does the author interrupt the story of Joseph to tell us about this seemingly unrelated incident with Judah? How does this passage reveal to us Judah's character. Why is that important? What was this whole thing about Onan fulfilling the "duty of a brother-in-law" by taking Tamar as a wife? What really was Onan's sin? What is this whole thing about levirate marriage all about? What did God think about it? What was Judah doing wrong with Tamar? How does this story fill us in on Israel's experience in Egypt? (53 min.)