Paul operates with a fellowship-driven mentality, as Israel’s history, defined by God’s covenant dealings with them, looms large in his thinking. So as we see him, because of God’s justifying activity, incorporating Gentiles into the stories of Adam and Moses to go along with their being incorporated into the story of Abraham, with each story marking the creation of a covenant people (which is also taking place in the church, through the covenant that is marked by belief in Jesus), a demand is placed upon us to allow these thoughts to resonate as we examine part of the fifth chapter of Romans.
The boundlessness of the covenant and of the grace of God (with that boundlessness not being undefinable or unobservable, but substantively demonstrated through the inclusion of Gentiles within that covenant) is set forth as Paul writes “But the gracious gift is not like the transgression” (5:15a). Remember, because Adam and Israel (Moses) are in view, “transgression” can be understood on multiple levels. Those multiple transgressions are overcome, however, “For if the many died through the transgression of the one man, how much more did the grace of the one man Jesus Christ multiply to the many!” (5:15b). We can point out that Paul believed Jesus, as Messiah (King/Christ), embodied Israel (it was a common understanding that the King stood in for the people), which allows for the transition from Adam to Jesus, encompassing Moses (who was standing in for Israel in this construct) in the process. Thus, we can see the movement from Adam, through Jesus, to the many---the Gentile nations.
Effectively, the covenant had been provided to all people through Adam, who represents all of humanity. Though this is probably an uncommon way of looking at God’s covenant dealings, and though it seems somewhat counter-intuitive on its surface, we can actually insist that God’s original covenant had been made with the whole of humanity, with Adam representing the whole. That covenant was eventually localized to Abraham and his descendants. This includes a number of nations, as we consider the very basic fact that Abraham had two sons, Ishmael and Isaac, both of which had a number of descendants.
The covenant with Israel represents a further localizing, as the descendants of Jacob, one of the numerous grandsons of Abraham, are chosen as God’s covenant people. According to the historical narrative on offer in Scripture, we see an ongoing narrowing of the covenant. What at first looks like an expansion, from Adam, to Abraham’s household, to Israel, is actually an ongoing process of restriction. The intentions always remained the same, however, which was to reflect God’s glory into the world and to gather up the praises of God’s creation and return them back to Him.
With the Assyrian conquest of Israel, and the dispersion of the northern ten tribes of the twelve tribes of Israel and their being scattered to the four winds, Judah remains on the playing field as the carriers of the covenant. This is yet another restriction. As we get closer to the time of Jesus, there is an even further narrowing of covenant participants, with groups within the land of Israel creating lines of demarcation that will determine which members of God’s historical covenant people are actually continuing to participate in God’s covenant.