For this is what the promise stated: “At the appointed time I will return, and Sarah will have a son.”
9. For the word of promise is this, etc. He adds another divine testimony; and we see, by the application made of it, with what care and skill he explains Scripture. When he says, the Lord said that he would come, and that a son would be born to Abraham of Sarah, he intimated that his blessing was not yet conferred, but that it was as yet suspended. Genesis 18:10.
The apostle, having made his way to that which he had to say, concerning the rejection of the body of his countrymen, with a protestation of his own affection for them and a concession of their undoubted privileges, comes in these verses, and the following part of the chapter, to prove that the rejection of the Jews, by the establishment of the gospel dispensation, did...
Commenting on Romans 9:6-13
And not only this,.... This instance of Ishmael and Isaac, is not the only one, proving that Abraham's natural seed, the children of the flesh, are not all children, the children of God: but when Rebecca also had conceived by one, even by our father Isaac, "it was said unto her", Rom 9:12, being in a parenthesis, "the elder shall serve the younger".