In Genesis chapter 25, we encounter another story which the New Testament employs as an allegory of certain principles of the Christian faith: Esau selling his birthright to Jacob. The story, told in Gen. 25:29-34, describes how Esau, the older of the twin brothers, came in one day from hunting and, famished from hunger, pledged to give his rights as the firstborn over to Jacob in exchange for some lentil stew. Now, the first thing that jumps out at many readers is the startling implication of this scene, which must mean either (1) that Esau's fondness for lentils, just about the most boring food ever, was a form of clinical insanity, or (2) that Jacob was the best cook the ancient world had ever seen. Or, as an alternate possibility, Esau was simply driven by his passions more than by his reason. This latter interpretation is the one you'll usually hear, but I'd still be curious to see Jacob's lentil recipe someday, because it may just be unthinkably fantastic.
In Romans 9, the apostle Paul uses the broader story of Jacob and Esau to illustrate the sovereign power of God. Though Esau was born first, God's sovereign intention was not thus restrained, and Jacob became the patriarch of God's chosen people Israel. As such, some interpreters in the Christian tradition have seen Esau selling his birthright as a foreshadowing of the way that the Jewish people would forsake their privileged position as the heirs of the covenant by choosing, at least in part, not to follow Christ, who was the fulfillment of their covenant. Indeed, Paul's use of the Esau/Jacob story in Rom. 9 is part of his larger exploration of why so many Israelites (but certainly not all) rejected the new covenant in Christ. Jesus himself is recorded in the Gospels making similar observations about the Jews' rejection of the covenant. Nonetheless, it's important to point out that even though such things are said in Scripture, they provide no warrant at all to antisemitic sentiments or actions--quite the contrary: Paul's discussion in Romans makes it abundantly clear that the loving hope of all Christians ought to be for the Jews to one day enter fully into the glory of the covenant that was prepared for them.
There's another possible foreshadowing, too, and this one doesn't include the distinction between the old and new covenants. Rather, it suggests that this story bears a hint of an important point in our theology of Jesus Christ's nature. Although Esau is a disappointing character in this story's original context, his act hearkens toward something that Jesus himself will do during the incarnation. The idea of a firstborn son laying aside his birthright as if it were not something to be held onto--well, that's an idea that plays out directly in the life of Jesus. In Philippians 2, Paul tells us that rather than seizing all the divine prerogatives of his identity as the "firstborn" Son of God, he "did not consider equality with God something to be used to his own advantage; rather, he made himself nothing by taking the very nature of a servant." In theology, this idea is sometimes referred to as the kenosis--the self-emptying of Christ, laying aside his own rights in order to enter the world at our level. He could have come to us with all the glory, power, and sovereign majesty that is his right as the eternal Son of God, but instead he laid it all down so that he could become like us. Though Esau's story derives from a very different context, the outward similarity of his thoughtless act to Christ's intentional humility should draw our minds and our hearts toward the reckless sacrifice of the incarnation of Jesus Christ. Like Esau's choice of lentils over his birthright, it's absolutely startling, almost nonsensical. Sometimes we lose sight of just what a staggering thing it is to believe that the ineffable God of the universe set his unbounded majesty aside in order to enter our world as one of us. Esau's story reminds us of the ridiculous, upside-down way that the story of God's appearance defied all reasonable expectation.
(Painting: "Esau Selling His Birthright," by Hendrick ter Brugghen, c.1627)