What does Romans 9:7 mean?
Not everyone physically descended from Israel actually belongs to Israel. That's what Paul wrote in the previous verse. He seems to have meant something similar to what he wrote in Romans 2:28 that "no one is a Jew who is merely one outwardly." The spiritual aspect of our relationship with God is far more important than our ethnicity, heritage, or biology.Now Paul begins to give examples from Israel's history to clarify his point. To begin with, not all of Abraham's offspring were counted as the "children of Abraham." Some of them were not included in God's promises to Abraham's descendants. Both Abraham's son Ishmael, born before Isaac (Genesis 16), and his sons with Keturah, born long after Isaac (Genesis 25:1–4) were excluded from Israel.
Paul quotes from Genesis 21:12 where God said to Abraham that it is through Isaac that his offspring will be named. Jesus made similar remarks to His critics, as recorded in the gospel of John (John 8:36–39).