Understanding the Conflict we are In by Dr Michael H Yeager

In Galatians 4:28-29, Paul makes it clear that Ishmael represents the believer’s first birth (the flesh) and Isaac represents the second birth (the Spirit). Ishmael was “born of the flesh” because Abraham had not yet “died” and was still able to beget a son (Gen. 16). Isaac was “born of the Spirit” because by that time his parents were both “dead” and only God’s power could have brought conception and birth. Ishmael was born first, because the natural comes before the spiritual (1 Cor. 15:46).

When you trust Jesus Christ, you experience a miracle birth from God (John 1:11-13), and it is the work of the Holy Spirit of God (John 3:1-8). Abraham represents faith, and Sarah represents grace (Gal. 4:24-26), so Isaac was born “by grace … through faith” (Eph. 2:8-9). This is the only way a lost sinner can enter the family of God (John 3:16-18).

It is worth noting that, in the biblical record, God often rejected the firstborn and accepted the second-born. He rejected Cain and chose Abel (Gen. 4:1-15). He rejected Ishmael, Abraham’s firstborn, and chose Isaac. He bypassed Esau, Isaac’s firstborn, and chose Jacob (Rom. 9:8-13), and He chose Ephraim instead of Manasseh (Gen. 48). In Egypt, the Lord condemned all the firstborn (Ex. 11–12) and spared only those who were “twice-born” because they were protected by faith in the blood of the lamb.