Charles Spurgeon Commentary Galatians 3:6-7

"Even as Abraham believed God, and it was reckoned unto him for righteousness. Know therefore that they that are of faith, the same are sons of Abraham." — Galatians 3:6-7 (ASV)

Even as Abraham believed God, and it was accounted to him for righteousness. Know ye therefore that they which are of faith, the same are the children of Abraham.

He was the father of the faithful—that is, of the believing—not of those who trust in their own works. These are only like Ishmael, who must be cast out of the chosen family; but the true children, the real Isaacs, are those who are born according to the promise of grace.