Prior to moving along, and to fulfill a promise made earlier, we are in need of reviewing the story of Abraham in relation to God’s covenant with him and covenant speeches made to him. We must do so in order that, as would be the case for the Jewish part of Paul’s hearers (because it partially defined them), and also the Gentile portion of Paul’s hearers (because they were being grafted into the family of Abraham and so defining themselves and their purpose in the world accordingly), the story of Abraham is fresh in our minds and we are able to hear Paul within the appropriate Abrahamic context.
All of the subsequent covenant speeches to Abraham are conditioned by God’s original covenant speech that is on offer in Genesis twelve. Likewise, those covenant speeches, with their covenant promises and obligations, are conditioned by God’s covenant speeches to both Adam and Noah, as those convey God’s original intentions for His creation and His divine-image bearers, with those intentions being implied in the words to Abraham as they are heard within the narrative that begins with Genesis one.
The second time God speaks to Abraham is recorded in Genesis thirteen. There, the Creator God says to Abraham, “Look from the place where you stand to the north, south, east, and west. I will give all the land that you see to you and your descendants forever. And I will make your descendants like the dust of the earth, so that if anyone is able to count the dust of the earth, then your descendants also can be counted. Get up and walk throughout the land, for I will give it to you” (13:14b-17). Israel treasured this promise. In times of exodus and exile, of displacement and restoration, it echoes through their history and it is clung to in hopefulness and as a sign of God’s covenant faithfulness.
In the fifteenth chapter of Genesis, “the wod of the Lord came to Abram in a vision” (15:1a). With that vision, the voice of God is heard saying “Fear not, Abram! I am your shield and the one who will reward you in great abundance” (15:1b). Abraham, who well understands the previous promises in regards to descendants and what is implied by abundance, while remaining childless, responds to the Lord with “O sovereign Lord, what will You give me since I continue to be childless, and my heir is Eliezer of Damascus?... Since you have not given me a descendant,” as promised, “then look, one born in my house will be my heir!” (15:2) Interestingly, Abraham, unlike his descendants of Jesus’ and Paul’s day, understood that physical descent was not of the utmost importance. Abraham well knew that, according to the custom of his own day (and that of subsequent eras), that being a member of a man’s household, if adopted as his son with full rights of sonship, made the adopted one equal to a born son. Surely Paul has this in mind as he speaks of Gentiles joining the house of God that began with Abraham.
However, “the word of the Lord came to him, ‘This man will not be your heir, but instead a son who comes from your own body will be your heir” (15:4). Though an heir through adoption would have been perfectly legitimate, God has chosen to go the route of natural sonship, with the added benefit that, because of the advanced age of both he and his wife, trusting in this promise will be difficult for Abraham, while it also proves up the power of this covenant-making God. Reiterating His previous words of promise and adding another metaphor of immeasurability, “the Lord took him outside and said, ‘Gaze into the sky and count the stars---if you are able to count them!’ Then He said, ‘So will your descendants be” (15:5). To this the author of Genesis adds, happily for the man who has been given the responsibility of taking the Gospel to the Gentiles, “Abram believed the Lord, and the Lord considered his response of faith as proof of genuine loyalty” (15:6).
Because the Gospel of Jesus demands a response of loyalty to the proclaimed King, just as the gospel of Caesar demanded a response of loyalty to the proclaimed king, Abraham’s response to the assertion of God’s power and faithfulness, which was belief, is directly analogous to the situation of Gentiles. Luckily for Paul, he does not need to proof-text, as the story of Abraham is ingrained and well-rehearsed. Those who may oppose his works-of-the-law-free justification message are going to have difficulty responding to this all-important point of Abraham’s story. For all practical purposes, Abraham is ensconced in the language and state of justification (righteousness), and circumcision is nowhere in sight (still two chapters and at least thirteen years away).