Isaac also had a couple of sons—twins, as a matter of fact.
To Rebecca, also, a promise was made that took priority over genetics. When she became pregnant by our one-of-a-kind ancestor, Isaac, and her babies were still innocent in the womb—incapable of good or bad—she received a special assurance from God. What God did in this case made it perfectly plain that his purpose is not a hit-or-miss thing dependent on what we do or don’t do, but a sure thing determined by his decision, flowing steadily from his initiative. God told Rebecca, “The firstborn of your twins will take second place.” Later that was turned into a stark epigram: “I loved Jacob; I hated Esau.” (Romans 9:10-13)
Here we find Jacob and Esau. Esau became the father of a great nation, as did Jacob. However, God chose Jacob before he was born. He was the recipient of promise because of nothing other than the choice of God. This reveals that it is not by posterity, nor is it by works; it is by the promise and the sovereign elective choice of God.
This brings us to a second question. In verses 14-16 we read,
Is that grounds for complaining that God is unfair? Not so fast, please. God told Moses, “I’m in charge of mercy. I’m in charge of compassion.” Compassion doesn’t originate in our bleeding hearts or moral sweat, but in God’s mercy. (Romans 9:14-16)
And he points to Moses before Pharaoh as his illustration.
The same point was made when God said to Pharaoh, “I picked you as a bit player in this drama of my salvation power.” All we’re saying is that God has the first word, initiating the action in which we play our part for good or ill (Romans 9:17-18)
Twenty times in Scripture it says that God hardened Pharaoh’s heart. Sometimes we think, “Well, that’s not fair.” That is the very question Paul is trying to answer: “Is God unjust?” How is it just for him to harden our hearts and then to blame us and condemn us for having hard hearts?
As you study that illustration of Pharaoh, God only allowed Pharaoh’s heart to be permanently set in his evil ways, the way that Pharaoh chose. In other words, God does not harden our hearts against our will, he simply allows us to have our own way, even when it is abject rebellion against the Holy God of the universe. Go back to the first two chapters of Romans and see that very thing. God lets us choose, even to the point where we become set, irrevocably set, in our way, and that is what happened to Pharaoh. God gave Pharaoh opportunity after opportunity to let Israel go, chance after chance. The question is this: “Did Pharaoh deserve even one chance?”
We are all born in sin, and that is a fact we try to forget. We do not deserve anything from God. If we get what we deserve, we get eternal damnation. Pharaoh chose 10 times to reject and rebel against God. He was a sinful being, not only by nature, but also by choice. To say God hardened his heart is simply to say that God allowed him to follow his own will.
If interested, you can download the entire study of The Letter to Christians at Rome