6 Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel: 7 Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called. 8 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. 9 For this is the word of promise, At this time will I come, and Sara shall have a son. (Romans 9:6-9 KJV)
William Burkitt’s Commentary
Here Apostle Paul answers an objection against the rejection of the Jews: “If they cast off by God, what will become of the promise of God, made to Abraham, saying, I will be thy God, and the God of thy seed?
He answers, by distinguishing a two-fold seed that Abraham had. Some were only his carnal seed or the children of his flesh; others were his spiritual seed or the children of his faith.
Now the carnal seed of Abraham, born according to the course of nature, were not the children of God to whom the promise was made, but the children represented by Isaac, born by the supernatural power of the Spirit of God; these are to be accounted the true seed of Abraham, mentioned in the covenant when God says, I will be thy God, and the God of thy seed.
So that the force of the apostle’s argument lies thus: The rejection of such Jews, or such of Abraham’s seed only who were so according to the flesh, cannot make the word or promise of God to Abraham and his seed of no effect, because he made no absolute promise to them as such.
But, says the apostle, none of those Jews, whose rejection I speak of, have any such promise made to them; therefore the rejection of some of Abraham’s natural seed doth not, cannot make void the word and promise of God.
Learn hence, 1. That the promises of God to his children and people are firm and stable; they shall not be made void, but be accomplished and made good to those that have a title to them, and interest in them, and fulfil the conditions of them: not as though the word or promise of God has taken no effect, all are not Israel that are of Israel.
Learn thence, 2. That as all were not true Israelites of old that did bear the name of Israelites; so all are not true Christians at this day, who take upon them the name of Christ, and bear the name of Christians.
Learn, 3. That men are very prone to bear up themselves upon the piety of their ancestors, though strangers, in practice, to their piety; as the Jews boasted they were the seed of Abraham, but did not the works of Abraham, but did not the works of Abraham; whereas men are so far from being God’s children, because they had godly parents, that Christ told the Jews, who came forth out of Abraham’s own loins, that they were of their father the devil. Joh 8:44.