Matthew opens by naming Jesus son of Abraham. The promise was never a closed blood-club. From Genesis 12 the nations were in view.
God told Abraham that in his seed all families of the earth would be blessed. Paul later reads that seed as Christ, and those who belong to Christ as Abraham’s family. Circumcision and Sinai came later as administration, not as the original definition of the heirs.
The contrast is not “Abraham versus the church.” It is promise versus flesh-line as the final boundary. Isaac already taught that: the child of promise, not merely the child of the body, carries the calling.
Matthew 1 plants Abraham in the first verse so the Gospel cannot be read as a surprise departure from Israel’s story. The King is Abraham’s son. Then the book keeps widening the table: Magi, a centurion, a Canaanite woman, a commission to the nations.
When Jesus says many will come from east and west and recline with Abraham, He is announcing that the Abraham promise has reached its hour.
In the apostolic generation the nations were already being named children of Abraham by faith. Romans 4 and Galatians 3 treat the family as present. AD 70 removed the temple system that had been used to keep the old boundary in force.
If you are in Christ you are Abraham’s seed. The paperwork of flesh is not what keeps you in the family.