Paul asserts that the law came much later than God’s promise to Abraham and the promise is like unto a last will and testament. God gives the blessing to Abraham and it is to be understood as an inheritance. (Genesis 12:7, 22:17-18) Since the promise was before the law then the promise belongs to the Gentiles also.
The law came 430 years after the promise to Abraham. (Exodus 12:40) Paul asks us to take a closer look at the promise of Abraham to see that the Torah wording is particularly concise. The promise does not say, “And to offsprings,” as in many people. The promise says, “And to your (Abram and Sarai) offspring,” a singular word that indicates there is one Offspring to come from the promise and that is Christ Jesus.
The blessings of Abraham and Sarah move through the generations until God’s Plan is put into place and Jesus is born to us. He is the Offspring. God gives our inheritance by promise, not by Law. Christ is the heir of the promise to Abraham.
Paul knows that there are many children from Abraham which make up the lineage of Jesus. Paul’s pointing us to the Grace of God given to us through the promise of Abraham. Paul’s thoughts will culminate to, “And if you belong to Christ, then you are Abraham’s offspring, heirs according to the promise.” v. 29. The promise affirms that Christ is for all of us, no matter where our National roots are found or what our DNA reveals. Salvation for all is in Christ Jesus.
15 Brothers and sisters, I give an example from daily life: once a person’s will has been ratified, no one adds to it or annuls it. 16 Now the promises were made to Abraham and to his offspring; it does not say, “And to offsprings,” as of many; but it says, “And to your offspring,” that is, to one person, who is Christ. 17 My point is this: the law, which came four hundred thirty years later, does not annul a covenant previously ratified by God, so as to nullify the promise. 18 For if the inheritance comes from the law, it no longer comes from the promise; but God granted it to Abraham through the promise. Galatians 3:15-18