The advantage of reading the Bible, rather assuming what it says, is that we find sinners a lot like us. When Joseph’s brothers were going to kill him, Judah convinced them to make a buck by selling him into slavery instead. With Joseph out of the picture, he is the leader among his brothers, but not for good. In this story God breaks through his sin in the unlikeliest way, and establishes Tamar not just as a mother in Israel, but also as an ancestress of Jesus Christ.