Look these facts in the face. If any man is fully persuaded as regards himself that he belongs to Christ, let him consider again with himself, that just as he is Christ's, so also am I.

Abraham's

Notice then that the true sons of Abraham are children of faith.

For it is written that Abraham had two sons, one by the slave woman and one by the free woman;

He is the father of circumcision to those who are not merely circumcised, but who also walk in the steps of that faith of our father Abraham which he held while he was as yet uncircumcised.

they are not all children of Abraham because they are Abraham's descendants. The promise was, In Isaac shall thy posterity be called.

of whom it had been said, It is through Isaac that your posterity will be traced.

Heirs

So each one of you is no longer a slave, but a son, and if a son, then an heir, too, through God's grace.

For the promise that he should be heir of the world did not come to Abraham or to his posterity through law, but through faith-righteousness.

and if children, then heirs, heirs of God and joint-heirs with Christ; but to share his glory, we must now be sharing his sufferings.

Paul, Apollos, Cephas, the world, life, death, things present or things to come; all things are yours;

namely, that in Christ Jesus the Gentiles form one body with us the Jews, and are coheirs and copartners in the promise, through the gospel.

In order that being justified by his grace, We might be made heirs according to the hope of eternal life.

Are they not all ministering spirits, sent forth for service in behalf of those who are about to inherit salvation?

On which principle God, wishing to show more convincingly to the heirs of the promise the immutability of his purpose, mediated with an oath;

By faith Noah, warned of God of things not yet seen, reverently gave heed, and built an ark for the saving of his house; by which he condemned the world, and became an heir of the righteousness which is of faith.

Listen, my dear brothers, has not God chosen the poor of this world to be rich in faith, and to inherit the kingdom which he has promised to those who love him?

He who overcomes will inherit these, And I will be his God, And he shall be my son.

General references

Is God then the God of the Jews alone, and not of the Gentiles also? He is God of the Gentiles also,

So then they who are children of faith are blessed with Abraham the faithful;

But you, brothers, are like Isaac, children of the promise;