It is assuredly an amazing thing that nearly all the firstborn in all of sacred history were unfortunate. In Egypt all the firstborn were slain by God. This seems to be the reason why the Law is conditional and those who have the Law generally become worse. They are proud on account of the Law, as though it has been given to nourish pride in the right of the firstborn, whereas it has been given to humble that pride. Therefore the arrogance and insolence of the firstborn was checked by God when they abused their honor and dignity. For all that was done and said looks to the unique firstborn Son of God, Jesus Christ, and His alone is all glory, might, and power. Now let us turn to the generation of Esau.
Luther’s works, vol. 6: Lectures on Genesis: Chapters 31-37 p 285-286