Throughout Genesis—and the entire Scripture for that matter—the God of promise is portrayed as stronger than the obstacles that arise as a result of the unfaithful actions of His people. These chapters of Genesis contribute significantly to a theology affirming the sovereignty of God over our periods of unfaithfulness; here then we find great encouragement. First it is clear that even through our failures of faith, God will fulfill His program of redeeming His people. Yet, we must also recognize that every episode of unfaithfulness brings shame, despair—and even danger—to ourselves and those we love. Thus, we must never use the Sovereignty of God as an excuse for our sin (Jas 1.13-15)

Here the primary obstacle to God’s promise is the sin of unbelief. The three heavenly visitors came to Abraham in Genesis 18 in accord with the LORD’s affirmation that Abraham and Sarah would conceive a child together—even though they “were old and getting on in years,” and “Sarah had passed the age of childbearing” (v. 11). Sarah takes center stage in this scene, and her unfaithfulness is revealed in sarcastic laughter (v. 12); but God was not joking. His response set forth the theme of salvation for all who will look beyond their total inability to a God who is faithful to His word; He asked, “Is anything impossible for the LORD?” (v. 14; cf. Lk 1.37).

While God is able to give extremely elderly people the ability to conceive a child, He is also competent to deal justly with the wicked. In the next scene, these three visitors mediate, along with Abraham, God’s condemnation of Sodom and Gomorrah (18.16-33). Abraham’s series of faithful inquiries may have underlying family concerns, namely the residence of his nephew in a place sentenced to destruction (19.1). It is not incongruous then that the biblical author would devote so much attention to Abraham’s petitions; the patriarch had a personal stake in what happened with any righteous ones found in Sodom and Gomorrah.

While Genesis 18 records Sarah’s failure, Genesis 20 details Abraham’s unbelief—before king Abimelech. Here Abraham lacked faith that God would indeed bless and protect him (cf. 12.2-3), confessing later to Abimelech: “I thought, ‘There is absolutely no fear of God in this place. They will kill me because of my wife’” (20.11). Abraham’s lack of steady dependence upon the God of promise caused him to cower before man. That Abimelech sent Abraham away with riches should remind us that God was not done with the patriarch—even though he had once again failed a test of faith (cf. Genesis 12).

Finally, after 25 years of waiting, Abraham and Sarah were biological parents of a son (cf. 12.4 and 21.5). Sarah’s response represents the joy of all who experience God’s faithfulness despite seasons of unbelief: “God has made me laugh, and everyone who hears will laugh with me” (21.6). And through the remainder of the chapter this joy is the experience of Abraham and Sarah—despite the expulsion of Hagar and Ishmael (21.8-21), and the tension of the land-covenant with Abimelech (21.22-34).

When we follow the episodes and themes of these chapters down the storyline of Scripture, we see that Paul used them to help the churches of Galatia understand Christian freedom from the Mosaic law. In Galatians 4 Paul again employed episodes from the life of Abraham in Genesis 16-21, arguing that the patriarch’s first two children were respectively related of the old and new covenants. Hagar, the mother of Ishmael, conceived through the natural laws of procreation (Genesis 16), and she thus corresponded to Mount Sinai and the Mosaic law (vv. 24-25). But Sarah, who conceived in her old age, received her child by promise and faith (Genesis 21). In this way, Paul argued, Ishmael was the child of slavery to the Law, Isaac the child of freedom and promise (vv. 26-30). Paul proposed that believers are children of promise, corresponding to the child of promise, Isaac, while those desiring to be under the Mosaic law are slaves, corresponding to the child of Hagar, Ishmael. Abraham’s fleshly act with Hagar represented a lack of faithful living; by submitting to the Mosaic law and circumcision the Galatians were in danger of succumbing to a life of slavery. Paul wrote:

“Tell me, you who want to be under the law, don’t you hear the law? For it is written that Abraham had two sons, one by a slave and the other by a free woman. But the one by the slave was born according to the flesh, while the one by the free woman was born as the result of a promise. These things are illustrations, for the women represent the two covenants. One is from Mount Sinai and bears children into slavery—this is Hagar. Now Hagar is Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free, and she is our mother” (Gal 4.21-26).

Those attempting to display their faith in Christ through the Mosaic law had no hope of eternal inheritance, and in this light we can see the urgency of Paul’s admonition to them; he quoted from Genesis 21: “Throw out the slave and her son, for the son of the slave will never inherit with the son of the free woman” (Gal 4.29; cf. Gen 21.10). Paul urged his readers to live by faith, not the Law, saying: “Brothers, we are not children of the slave but of the free woman” (Gal 4.31).


*For a complete list of references, please see