How can Ishmael and Isaac both be descendants of Abraham and yet not both be his “seed”? “It is God’s choice and calling that matters” and God chooses whose seed will carry on and how. The promise given to Abraham and his seed does not simply work through the line of descent. As Dr. Lloyd-Jones reminds, “the promise produces its own children.” Trace this history of Abraham and rejoice in Isaac’s miraculous birth “after the Spirit.” In this sermon on Romans 9:6–9 titled “Child of the Promise,” Dr. Martyn Lloyd-Jones addresses how miracles do not break the laws of nature, but rather they use the laws of nature. It is God who produces the children of the promise. Election comes before production – Isaac was chosen before he was even born. Born of the flesh, yet born of the Spirit. Listen as Dr. Lloyd-Jones looks at both the Old and New Testament accounts of this. These are the two covenants and have huge implications. What matters is that one is born of God.

http://www.mljtrust.org/sermons/child-of-the-promise/