Summary: Everything depends on God’s Mercy
The Bible teaches Election
And this gets to a very deep and difficult teaching found throughout the Bible, the teaching of election, and God’s choice of some people over others.  Jesus use to tell His followers repeatedly, ‘You did not choose me, but I chose you’,  and, ‘I have chosen you out of the world.’ 
The doctrine’s difficulty
It is difficult teaching. It is difficult to explain from a human standpoint. Before the twins were born, God choose one over the other. 
We don’t have to live very long as a Christian to realize that God does not feel the need to resolve all our questions about every puzzling event that happen to us in this life. How many times in life have you asked God ‘why’ and the reply has been silent? God does not despise our honest questions. But at the same time He obviously doesn’t answer all our questions either.
An explanation of Election
The Bible teaches that on some level God chooses His people.  We like to think, ‘I choose Christ’. And that is true up to a point. But on some level the Bible also teaches that God choose you. That is why you are sitting here this morning. The Bible never says anything like, ‘God chose Bill and Bob for Heaven and Cindy and Sue for Hell’. But it does talk about God choosing His people for mysterious purposes. Like here where he choose Jacob over Esau before they were born for some mysterious purpose. Why He chooses us is a mystery. But He chooses us. Is God playing favorites? Well not necessarily. The explanation of election with the fewest problems  is that God does not so much choose individuals, but rather He chooses ‘Believers’, the group, ‘whosoever will have faith in God’s Son.’ Another way to say that is, ‘Through His foreknowledge the Father chooses, ‘whosoever will accept His Son’, and the kind of eternity that God offers through Christ.’ The Bible teaches that God wants everyone to be saved. There are dozens of verses to that effect.  And it speaks of the Father searching for men.  But the kind of life God is offering through Christ looks a certain way. It is an eternity wrapped around God and neighbor. And not everyone wants that kind of future. So God lets people have their fill of their own ways. In fact He helps them along their way. But He chooses those He knows will accept Him.
Trust God here
Really the idea of election isn’t all that problematic if you who have faith in God. God is fair and just in all His ways. We believe that even if we don’t understand it. And in the end His mysterious purposes will be revealed to be merciful.
Paul’s point here is that there has always been an election within election
But really what is Paul is getting at here in Romans 9 is that there is an election within an election. The heirs of faith were always a subset within ethnic Israel. That is true among church members too. Just being a member of the church doesn’t save anyone, although it has certain privileges. But Paul’s point is clear, that the children of promise, spiritual Israel, the ‘Israel of God’, were never the same as ethnic Israel. They were always a subset if you will.