At that time, Israel was, for the larger part, observing the requirements of the law, but because it was being used as a boundary (keeping non-Israelites outside of the covenant) rather than as an aid to blessing the nations (bringing non-Israelites into the covenant), their God was still not receiving the glory that He desired. Indeed, they were falling short, and seemed to be doing it willfully and proudly. Jesus comes on to that the scene and condemns this sin of what was then termed as the “works of the flesh” (circumcision, food laws, Sabbath keeping --- what the “big three” of the law had become), which were being ardently held to as a means of identifying those that were truly God’s people and who would be the beneficiaries of God’s expected action on behalf of His people. This apparently continued to defeat God’s ultimate purposes for Israel, for His creation, and for the people of a renewed Israel (from every tribe and tongue) that He had chosen for Himself from before the foundations of the world.
The condemning of this sin of the flesh was brought about “so that the righteous requirement of the law may be fulfilled in us.” This “righteous requirement” pointed to the plan, rooted in God’s covenant faithfulness (first revealed to Abraham so as to reverse that which was wrought by Adam), to extend His blessings to all peoples, doing so through the medium of His covenant people, functioning properly. Through His faithfulness, represented by the faithful actions of His Messiah (Jesus of Nazareth), the Creator God was able to fulfill what it was that was required by His covenant, which was the creation of a covenant family that would encompass the peoples of the world.
This covenant family would represent the living, breathing, serving kingdom of God, as in union with His Messiah through a trusting allegiance and belief in Him as the crucified and resurrected King of the entire cosmos, they would be a people willingly submitted to Him as Lord. This submission would work itself out in countless daily actions, and it crossed all boundaries of race, ethnicity, class, and social status, showing itself as the anti-thesis of that to which Israel had been holding to through that day.
Rounding out the thought of the fourth verse of Romans eight, it can be seen that the righteous requirement is fulfilled in those “who do not walk according to the flesh but according to the Spirit.” This reinforces the point that has been being made, in that the Creator God’s covenant faithfulness is demonstrated, not in those who wanted to set up systems and hold to traditions of exclusivity, doing this in accordance with the flesh (works of the flesh ---- circumcision, food laws, Sabbath keeping --- and there is no sense here of earning God’s favor or earning heaven); but rather, God’s covenant faithfulness is demonstrated by those that walk according to the Spirit. Those that are apparently brought to faith and belief by the activity of the Holy Spirit, believing in the Gospel of Jesus Christ, are a new creation in union with Christ. The works of the flesh (circumcision, etc…) were now irrelevant in identifying those that were in covenant with the Creator.
It is this new creation, empowered by the same Spirit that raised up Christ from the dead, that are those through whom the Creator God now works to continue to extend His covenant and bestow His blessings, with this accomplished first and foremost through the preaching of the Gospel (which must include crucifixion and Resurrection), which of necessity includes the living out of the Gospel. As one continues to think about the works of the flesh that made for a continual separation of Israel from other peoples, one must also acknowledge that part of the work of the Spirit is the tearing down of those walls, so that “There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female---for all of you are one in Christ Jesus. And if you belong to Christ, then you are Abraham’s descendants, heirs according to the promise” (Galatians 3:28-29).