Kehillah in Rome 9:6-8

Orthodox Jewish Bible

⁶ But it is not as though the Dvar Hashem has failed. For not all those descended from Yisroel are truly redeemed Yisroel (of the eschatological Geulah Redemption).

⁷ Nor is it as though all the banim of K’lal Yisroel are the ZERA of Avraham Avinu, but (as it is written) BEYITZCHAK YIKARE L’CHA ZERA ("In Yitzchak shall your seed be called, named, summoned" BERESHIS 21:12).

⁸ That is, it is not the b’nei habasar (old humanity without hitkhadshut) who are the b’nei HaElohim (children of G-d) but the b’nei HaHavtachah (children of the promise) who are reckoned as ZERA (seed, children, including the right of the heir in relation to the father).