Galatians 3:7 - Matthew Poole's English Annotations on the Holy Bible

They which are of faith; those who are believers, and receive Jesus Christ, as exhibited and tendered to them in the gospel, trusting not to any righteousness of their own, arising from their obedience to the works of the law; they are the children of Abraham, considered as the father of the faithful, that is, they are justified as Abraham was justified; who was justified, not by his circumcision, but upon his believing in Christ exhibited to him in the promise; not by working, but by imputation. This argument came very close to the Jews, whose great glorying was in having Abraham to their father; for it is in effect a saying, that they were no true children of Abraham, none of that seed to whom the promise was made, if they expected justification from the works of the law, which Abraham never had nor expected.