Romans 9:6 : But it is not as though the word of God bath come to nought. For they are not all Israel, that are of Israel. The condition of fleshly Israel, though not clearly stated in Romans 9:1-5, was, nevertheless, im-plied. But the fact that fleshly Israel had rejected Christ, and were therefore anathema from Christ, did not show that the word of God--the promise to Abraham had come to nought. Romans 9:7 shows that the promise made to Abraham is the word of God that Paul had in mind. Even though fleshly Israel had rejected Christ, there was yet a spiritual Israel, and the promise was fulfilled in them.
Paul's language in these verses shows that the promise made to Abraham terminated in spiritual Israel. They do greatly err who think the promise to Abraham is yet to be fulfilled in fleshly Israel. Blood descent from Abraham does not entitle one to share in the promise.