Remember this too: later, Isaac's wife, Rebekah, gave birth to twins. Those two sons had the same father, who was our ancestor, Isaac. And God spoke to Rebekah before her sons were born. God spoke before the boys had done anything either good or bad. God did this to show clearly that he himself was choosing one child. He was not choosing someone because of what that person had done. He himself decided which one he would choose. God said to Rebekah, ‘The older son will serve the younger son.’ This is written in the Bible: ‘I loved Jacob, but I hated Esau.’
Because of this, someone might say that God is not fair. No! We should never say that! Remember that God said to Moses, ‘I will be kind to whoever I choose to be kind to. I will feel sorry for whoever I choose to feel sorry for.’
So then, it is God who decides these things. It is not because of what people want. It is not because of what people do. It is because God chooses to be kind.
Romans 9:10-16