Gal 4:
22 For it is written that Abraham had two sons, one by a slave woman and one by a free woman. 23 But the son of the slave was born according to the flesh, while the son of the free woman was born through promise.
The contrasts:
- slave and free
- flesh and promise
Who is the son of the free and the promise?
28 Now you brothers, like Isaac, are children of promise.
Isaac, and by spiritual (not fleshly) extension, we Christians are also sons of the free and promise.
31 So, brothers, we are not children of the slave but of the free woman.
Paul elaborated on this spiritual extension in Rom 9:
6b For not all who are descended from Israel belong to Israel, 7 and not all are children of Abraham because they are his offspring, but “Through Isaac shall your offspring be named.” 8 This means that it is not the children of the flesh who are the children of God, but the children of the promise are counted as offspring.
Christians are children of the promises.
What are these promises?
Going back to Galatians, in Chapter 3:
14 so that in Christ Jesus the blessing of Abraham might come to the Gentiles, so that we might receive the promised Spirite through faith.
I.e., the indwelling Paraclete.
16 Now the promises were made to Abraham and to his offspring. It does not say, “And to offsprings,” referring to many, but referring to one, “And to your offspring,” who is Christ.
Christ is a promise from God to Abraham.
17 This is what I mean: the law, which came 430 years afterward, does not annul a covenant previously ratified by God, so as to make the promise void. 18 For if the inheritance comes by the law, it no longer comes by promise; but God gave it to Abraham by a promise.
Inheritance is another promise.
21 Is the law then contrary to the promises of God? Certainly not! For if a law had been given that could give life, then righteousness would indeed be by the law. 22But the Scripture imprisoned everything under sin, so that the promise by faith in Jesus Christ might be given to those who believe.
Faith in Jesus is another promise.
26 for in Christ Jesus you are all sons of God, through faith.
Gentiles could be sons of God, which is another promise.
27 For as many of you as were baptized into Christ have put on Christ. 28 There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. 29 And if you are Christ’s, then you are Abraham’s offspring, heirs according to promise.
Initially, Isaac was the son of the promise. Through Christ, believing gentiles become sons of the promises. Christians are to receive the indwelling Paraclete and eternal life.
