Romans 9:6 But it is not as though the word of God has failed. For not all who are descended from Israel belong to Israel,
Paul explains the covenant that God made with Abraham in Genesis 17 did not fail. It did not fail because the offspring referred to in Genesis 17:7 were the spiritual offspring of Abraham and not his physical descendents. While some of his physical descendents were also spiritual descendents, most of them were not [Romans 9:27]. Therefore the covenant promise of Genesis 17:7 was made to the spiritual people of God and not to the physical descendents of Abraham. Beginning here and continuing through verse 13 Paul thoroughly explains the covenant of promise made with his elect [Spiritual Israel].
Focus on Christ #136