"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." Romans 9: 6-8
An important part of New Testament and New Covenant doctrine is here in these three verses. Paul does not spell out in an explicit way the doctrine he is revealing here. And this means that the reader has to supply that which is not made explicit.
Not spelling out in detail all the implications of Romans 9: 6-8 means that false prophets can more easily deceive many into accepting a theology which contradicts these verses.
"For there must be also heresies among you, that they which are approved may be made manifest among you." I Corinthians 11: 19
For example,in the statement "Neither, because they are the seed of Abraham, are they all children," a false prophet can deceive many into thinking that Paul is not saying that all who belong to the physical chosen people bloodline are the children of God in the New Covenant. But that is exactly what Paul is saying.
Does Romans 9: 6-8 say anything which is relevant to dispensationalism's teaching that God now has two peoples, Israel, by which is meant Old Covenant Israel, and the Church?
The text does imply that part of Israel is God's people and a part of Israel is not God's people. This implies that what Paul calls the children of God are the elect of Israel in the New Covenant.
But what about non-Jews becoming also the children of God in the New Covenant? "And I will sow her unto me in the earth; and I will have mercy upon her that had not obtained mercy; and I will say to them which were not my people, Thou art my people; and they shall say, Thou art my God." Hosea 2: 23
Hosea 2: 23 began to be fulfilled in Acts 10 when Peter was sent to Cornelius and his people because God was to save those people who were not Jews.
Paul affirms that saved Jews and saved non-Jews are one people of God, not two peoples. "For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him." Romans 10: 12
"For ye are all the children of God by faith in Christ Jesus.
27. For as many of you as have been baptized into Christ have put on Christ.
28. There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
29. And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise." Galatians 3: 26-29
The implication of Romans 9: 6-8 is that the part of Israel which in the New Covenant received Christ by faith and were born again is the Israel of God (Galatians 6: 16), and another implication of Hosea 2: 23 and Romans 10: 12 supported by Galatians 3: 28 is that the non-Jews who received Christ and were born again are also the Israel of God,