Genesis 15-17 further establishes Abraham’s role in the metanarrative of Scripture. Paul employed the real-life events of Abraham to illustrate the blessings and allegiance that correspond to faith in Jesus Christ. By the time of Genesis 15, Abraham did not yet have a single blood-line heir—let alone enough posterity to be called a great nation as God had promised in Gen 12:2. Then the word of the Lord came to Abraham saying: “Look at the sky and count the stars, if you are able to count them…Your offspring will be that numerous” (Gen 15:5). Abraham responded with courageous faith and the Lord credited Abraham’s response as righteousness (Gen 15:6), establishing Abraham as the model of faith. God affirmed Abraham’s faith through the smoking fire pot and flaming torch—reminding the patriarch that he would not only become a great nation, but that his descendants would also dwell in the Promised Land (Gen 15:9-21).
Nevertheless, the first words of Genesis 16 reveal that Abraham was yet waiting on the fulfillment of God’s promise: “Abram’s wife Sarai had not borne him children” (Gen 16:1). Sarah interpreted God’s delay as a definitive act, saying, “Since the LORD has prevented me from bearing children, go to my slave; perhaps I can have children by her” (Gen 16:2). Abraham failed to respond appropriately in this crisis of faith and the result was not what Sarah had intended; rather than fulfilled, her life was made bitter by the birth of Ishmael to Hagar (Gen 16:4-7).
Genesis 17 records God’s covenant affirmation to Abraham, given years after Abraham’s unfaithful act with Hagar. God promised that He would bring many descendants from Abraham and Sarah’s union. To give Abraham a constant reminder of this promise, God changed his name from Abram to Abraham (“father of nations”) and promised again that Abraham’s descendants would have their own territory (Gen 17:1-8). God commanded Abraham to circumcise both of his sons (Gen 17:9-14). Thus, the anatomical locale of procreation was marked for God’s special purpose, reminding future generations that only by God’s help could their nation increase in number and carry on. The sign of circumcision reminded Abraham’s descendants that they were a special people, heirs of promise and faith. In Gen 17:15-22, God affirmed that the child of promise would be born to Abraham through Sarah—stating the exact time the child would be born.
The events in Genesis 15-17 provide the blueprint for understanding God’s redemptive plans. Paul saw in God’s promise to Abraham and the patriarch’s faith a framework for how sinful humans could be made right with God.
(1) In Romans 4, Paul wrote that sinful humanity’s inability to be right with God apart from divine intervention reflects Abraham and Sarah’s inability to conceive. In Rom 4:4-8, Paul wed the concept of faith expressed by Abraham (Genesis 15) with the theme of forgiveness in Psalm 32. Paul wrote that if someone works, payment is not a gift but what is owed to them. In Gen 15:6, however, God bestowed righteousness to Abraham on the basis of Abraham’s faith, before giving Abraham the covenant of circumcision in Gen 17:1-14. Paul saw in God’s kindness to Abraham a link with David’s description of the joy that comes upon those whose sins are covered (Ps 32:1-2).
(2) The bulk of Paul’s argument to the Galatians was based upon the record of Abraham in Genesis 15-17. In Gal 3:6-18, Paul set forth the faith (and justification) of Abraham to help the Galatians understand that they needed faith and the Spirit, not circumcision or obedience to the law, to be justified. Paul said the purpose of Christ’s work was “that the blessing of Abraham would come to the Gentiles in Christ Jesus so that we could receive the promise of the Spirit through faith” (Gal 3:14). The chronological flow of the Scripture storyline was fundamental to Paul’s argument: since Abraham received the promise of justification by faith more than 400 years before the law was given on Mount Sinai, all who had faith like Abraham became heirs apart from the law.