Children of the Promise

In the New Testament it is taught, not in poetic imagery, but didactically, in simple, unmistakable prose, that believers are the seed of Abraham; they are his sons; his heirs they are the true Israel. (See especially Romans 9 and Galatians 3) It is not natural descent, that makes a man a child of Abraham. "They which are the children of the flesh, these are not the children of God; but the children of the promise are counted for the seed." (Rom. 9:8.) The Apostle asserts that the promises are made not to the Israel κατα σαρκα, but to the Israel κατα πνευμα He says in the name of believers, "We are the circumcision." (Philippians 3:3.) "We are Abraham’s seed, and heirs according to the promise." (Gal. 3:29.) The promise to Abraham that he should be the father of many nations, did not mean merely that his natural descendants should be very numerous; but that all the nations of the earth should have the right to call him father (Rom. 4:17); for he is "the father of all them that believe, though they be not circumcised." (Rom. 4:11.) It would turn the Gospel upside down; not only the Apostle’s argument but his whole system would collapse, if what the Bible says of Israel should be understood of the natural descendants of Abraham to the exclusion of his spiritual children.

Hodge, C. (1997). Systematic theology.