"But we believe that through the grace of the Lord Jesus we shall be saved, even as they." How full of power these words! The same that Paul says at large in the Epistle to the Romans, the same says Peter here. "For if Abraham," says Paul, "was justified by works, he hath whereof to glory, but not before God." Do you perceive that all this is more a lesson for them than apology for the Gentiles? However, if he had spoken this without a plea for speaking, he would have been suspected: an occasion having offered, he lays hold of it, and speaks out fearlessly. See on all occasions how the designs of their foes are made to work with them. If those had not stirred the question, these things would not have been spoken, nor what follows.
Then he shows, not that the Law was evil, but themselves weak. "But we believe that through the grace of the Lord Jesus we shall be saved even as they." Mark how he ends with a fearful consideration. He does not discourse to them from the Prophets, but from things present, of which themselves were witnesses. For if, what the Law could not do, faith had power to do, "we believe that through the grace of the Lord Jesus we shall be saved even as they:" but faith falling off, behold, themselves are in destruction. "And put no difference between"-he said not, them of the circumcision, but "us and them," i.e. the Gentiles: for this gradual advance little by little is stronger.
You, who are enemies of this grace, reject the idea that we should believe that the people of old were saved by the same grace of Jesus Christ. Rather, you distinguish the different times in the manner of Pelagius in whose books this is found. You say that prior to the law they were saved by nature, then through the law and finally through Christ, as if for the human beings of the two earlier periods, namely, prior to the law and under the law, the blood of Christ was not necessary. In that way, you destroy the statement, “For there is one God and one mediator between God and humankind, the man Christ Jesus.”
But by the grace of the Lord Jesus Christ we believe to be saved, even as they are. If therefore they, that is, the fathers who could not bear the yoke of the old law, believed themselves to be saved by the grace of the Lord Jesus Christ, it is manifest that this grace was what made the ancient righteous live. Since the righteous shall live by faith, there could have been different sacraments for different times, yet all converging harmoniously to the unity of the same faith.
[AD 407] John Chrysostom on Acts 15:11