“Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel: Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called. That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed.” (Romans 9:6–8, KJV 1900)
I had a Jewish man come to me one time. He had a question regarding Christianity. Why did all Christians not act like Christians? He asked this because he knew a devout Christian who acted so much differently than others that he thought were Christian. Part of my answer was, “Not everyone who says they are Christian are Christian.” Of course, I had to go on and explain the Holy Spirit’s work of regeneration.
My answer to him, in a way, relates to Paul’s writing here regarding the Israelites. He says, “not all who are descended (in the flesh) from Israel belong to Israel.” He goes on to explain that those (Israelites) born of the flesh are not the children of God and that those of the promise are. Who are the children of the promise? They are those who have by faith been born of the seed of Abraham, who is Jesus the Messiah.
We should note that God gave the promise to Abraham before he had a son. To Abraham who was advanced in years and Sarah, his wife, having been barren and beyond child bearing years, this promise that through his seed all the nations of the earth would be blessed would have seemed impossible. Furthermore, the Lord tells Abraham that the promise would pass through Isaac.
Paul is demonstrating that God is sovereign over the salvation of people. In this sovereignty, God has decreed that a relationship with Him would come through the promise. You can imagine how the Jewish person of Paul’s day would have responded to this. Paul is saying to them that their earthly lineage cannot justify them before God and neither can their obedience to the Law. It is only by God’s sovereign promise that people are saved.
Those that have entered the promise, do so by faith, just as Abraham did. The Scripture indicates that Abraham believed God and it was counted to him as righteousness. Remember that God first called Abraham, giving him the promise and then he, Abraham, walked by faith according to the promise. The sovereign promise of God transformed his life, just as it does for believers today. God has called us to salvation and we have responded by faith. Thus, we have entered into the promise and have become the children of God.