Isaac and Ishmael: Spirit and Flesh (21:8-11)
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.
Isaac pictures the child of God not only in his birth but also in the joy that he brought. Isaac means “laughter,” and this time it was not the laughter of unbelief (Gen. 18:9-15). In the parables recorded in Luke 15, Jesus emphasized the joy that results when lost sinners repent and come to the Lord. The shepherd rejoiced when he found the lost sheep, and the woman rejoiced when she found the lost coin, and they both asked their friends to rejoice with them. The father rejoiced when his prodigal son came home, and he invited the neighbors to a feast so they could share in his joy. There is even joy in heaven when sinners turn to God (Luke 15:7, 10).
Nowhere do we read that Ishmael caused great joy in Abraham’s home. Abraham loved his son and wanted the best for him (Gen. 17:18). From before his birth, Ishmael was a source of painful trouble (Gen. 16), and after he matured, he caused even greater conflict in the family (21:9). The old nature is not able to produce the fruit of the Spirit, no matter how hard it tries (Gal. 5:16-26).
Note a third comparison between Isaac and the child of God: He grew and was weaned (Gen. 21:8). The new birth is not the end, but the beginning, and the believer must feed on God’s Word and grow spiritually (Matt. 4:4; 1 Cor. 3:1-3; Heb. 5:12-14; 1 Peter 2:1-3; 2 Peter 3:18). As we mature in the Lord, we must “put away childish things” (1 Cor. 13:9-11) and allow God to “wean us” (Ps. 131) from temporary helps that can become permanent hindrances.
The mother weans the child because she loves the child and wants it to be free to grow up and not be dependent on her. But the child interprets her actions as an expression of rejection and hatred. The child clings to the comforts of the past as the mother tries to encourage the child to grow up and enter into the challenges of the future. The time comes in every Christian life when toys must be replaced by tools and selfish security by unselfish service (John 12:23-26).
Like every child of God, Isaac experienced persecution (Gen. 21:9; Gal. 4:29). Ishmael was apparently an obedient son until Isaac entered the family, and then the “flesh” began to oppose “the Spirit.” It has well been said that the old nature knows no law but the new nature needs no law, and this is certainly illustrated in Abraham’s two sons.
Jewish children were usually weaned at about age three, so Ishmael was probably seventeen years old at the time (Gen. 16:16). What arrogance that a boy of seventeen should torment a little boy of only three! But God had said that Ishmael would become “a wild donkey of a man” (16:12 niv), and the prediction came true. The flesh and the Spirit are in conflict with each other and always will be until we see the Lord (Gal. 5:16-26).
When, like Isaac, you are born of the Spirit, you are born rich (Gen. 21:10). Isaac was the heir of all that his father owned, and God’s children are “heirs of God, and joint-heirs with Christ” (Rom. 8:17). Abraham cared for Ishmael while the boy was in the home, but “Abraham gave all that he had unto Isaac” (Gen. 25:5).
Finally, Isaac was born free, while Ishmael was the son of a slave (Gal. 4:22). Freedom is one of the key themes in Galatians (5:1) and one of the key blessings in the Christian life (4:31). Of course, Christian freedom does not mean anarchy; for that is the worst kind of bondage. It means the freedom to be and to do all that God has for us in Jesus Christ. “No man in this world attains to freedom from any slavery except by entrance into some higher servitude,” said Phillips Brooks, and that “higher servitude” is personal surrender to Jesus Christ. No one is more free than the child of God who delights in God’s will and does it from the heart.