Regard ye the things that are personal? If any man is confident in himself that he is Christ's, let him reflect again in himself, that as he is Christ's, so are we Christ's.

Abraham's

Know then that they who are of faith, these are the children of Abraham.

For it is written that Abraham had two sons, the one by a bondwoman, and the other by a free.

and the father of circumcision, not to those who are of the circumcision merely, but who also tread in the steps of the faith of our father Abraham, which he exercised while uncircumcised.

nor, because they are the seed of Abraham, are they all children: but, in Isaac shall thy seed be called.

unto whom it had been said, "That by Isaac shall there be a seed bearing thy name:"

Heirs

Therefore thou art no more a slave, but a son, and if a son, an heir also of God through Christ.

For not by the law [came] the promise to Abraham and his seed, that he should be heir of the world, but by the righteousness of faith.

But if children, then heirs; heirs indeed of God, and joint-heirs with Christ; if so be we suffer with him, that we may also together with him be glorified.

whether Paul, or Apollos, or Cephas, or the world, or life, or death, or things present, or things to come; all things are your's;

that the Gentiles should be co-heirs, and of the same body, and sharers with them of his promise in Christ by the Gospel:

that justified by his grace, we might become heirs in hope of eternal life.

Are they not all ministerial spirits, sent to perform service on account of those who are about to inherit salvation?

And thus God, designing more abundantly to demonstrate to the heirs of promise the immutability of his will, pledged himself by oath,

By faith Noah, being divinely warned respecting things not yet seen, filled with reverential awe, prepared an ark for the salvation of his household, by which he condemned the world, and became heir of the righteousness which is by faith.

Hear me, my beloved brethren. Hath not God elected the poor of this world to be rich in faith, and heirs of the kingdom which God hath promised to those who love him;

He that overcometh shall inherit all things, and I will be to him a God, and he shall be to me a son.

General references

Is he the God of the Jews only, and is he not also of the Gentiles? Yes, verily, of the Gentiles also:

Wherefore they who are of faith are blessed with believing Abraham.

So we, brethren, as Isaac, are the children of the promise.