Ishamael - Isaac
Esau - Jacob
Reoccurring theme. The firstborn sinful - the lastborn/second born righteous before God.
Jesus says "may the first be last and the last first"
Adam was the "firstborn" of God, but Jesus was the second/last born. Both were the only ones specially made/formed of God. All other people came from natural processes.
By the firstborn came sin and death (Adam's transgression), by the last born came righteousness and life (Jesus' atonement).
We (renewed through Christ) are the last (born of promise/born again) and does it not say that "the dead in Christ are raised first"?
We are the children of promise, the righteousness of God (as our forefathers Abel, Isaac and Jacob) and those under the law/before Christ are stuck with the curse of the firstborn Adam (as they are still the seed of firstborn - as all men are born in Adam that are not born in Christ).
A. Why we must be born again in Christ to free ourselves from the curse of the firstborn.
B. Why the blessings of the second born, are stressed by the reoccuring theme before Christ. So people would know that the second born (which are those under Christ as well as Isaac, Jacob and Abel) would inherit the promises of life.
Praise be to God!