Up until this point Paul has made the point that the Law “did not annul or add conditions to the promise God made to Abraham” (see William MacDonald’s, “Believer’s Bible Commentary”). So, using one of his favorite techniques for advancing his argument, Paul asks a question his readers will most naturally have in mind at this juncture: “Why then did God give the Law?”

The answer is “because of transgressions.” Notice, it doesn’t say, “because of sin.” Sin existed before the law was given, but, “ through the Law comes the knowledge of sin.” (Rom 3:20b). Consciousness of sin was heightened by the Law. In fact, Paul says, “… where there is no law, there also is no violation” (Rom 4:15). Put simply, the Law turns sin into transgression and accentuates it (Rom 5:20).

So, the Law did not annul the blessing. But it is also true that the blessing did not annul sin. God knew that in setting Abraham and his descendants apart as His special people there was a danger of their minimizing the significance of rebelling against God. Since the days of the Garden of Eden, humans have rebelled against their Creator and God’s plan of eternity has been to bring His image-bearers back to Himself. The promise to Abraham gave the great hope that has kept them from spiraling into nihilism and despair. The Law of Moses kept them from the myth that “I’m OK, You’re OK.” The promise leads us to look upward, and then to look inward. The first shows us our salvation, the second our need.

The law therefore cannot be added to the promise to effect salvation or even to enhance or preserve it. It was, in fact, a temporary measure, useful until Christ (the “seed”) came. Whereas the promise was made directly to Abraham, the Law was given to Moses through angels (see Heb 2:2). The Law was a bi-lateral agreement, involving responsibilities by two parties (God and the Israelites). The promise was unilateral, involving only one party with responsibility, namely God. Abraham and his descendants are beneficiaries of this agreement, but they had no responsibilities. There was no mediator in the promise to Abraham, since God is the single party involved (see Heb 6:13-18). What a magnificent plan for showing our need and giving us hope!