The Abrahamic covenant: dual in nature; one of works, one of
grace – each expressed in four ways. Two sons; one of bondage, the other of
promise. Two lands of promise; one of earthly shadows, one of heavenly
realities. Two circumcisions; one of the flesh, granting membership in the
Mosaic Covenant; one of the heart, granting people entrance into the New Covenant.
Two peoples; children according to the flesh, and those according to the
promise, marked by the circumcision not made by human hands – the unconditional
promise of God to His elect.