The Providential Preservation of Progeny and Promise

Have you noticed how the story of Judah and Tamar seems to interrupt the story of Joseph? It just doesn't seem to fit as you are reading through Genesis. Why is it here? What are we supposed to learn from this? A careful look at the texts reveals a near end to the tribe of Judah, whom the promised Savior will come. However, despite the sinful acts of Judah and Tamar, God's providential preservation of progeny and promise.