BROTHERS and SISTERS, glory and honor and peace for everyone who does good, to the Jew first and also to the Greek because there is no prejudice with God. Therefore, all who have sinned apart from the Law will also perish apart from the Law, and all who have sinned under the Law will be judged by the Law. For it is not the hearers of the Law who are righteous before God, but the doers of the Law who will be justified. When Gentiles, who do not possess the Law, do by nature what the Law requires, they are a law to themselves, even though they do not have the Law. They show that what the Law requires is written on their hearts, to which their own conscience also bears witness, and their conflicting thoughts will accuse or defend them on the day when, according to my gospel, God, through Jesus Christ, will judge the secret thoughts of all people.
Saint John Chrysostom explains how the doers of the Law will be justified,
Saint Paul makes inquisition, not into the quality of persons, but into the difference of actions. By so saying, he shows that it was not in actions, but in persons only, that the Jew differed from the Gentile. For it is not because one is a Jew and the other a Gentile, that on his honored and the other disgraced, but it is from the works that either treatment comes. He shows not only the equality of the Jew and the Gentile, but that the Jew was even much burdened by the gift of the Law. For the Gentile is judged without law. But this 'without law' here expresses not the worse plight, but the easier, that is, he does not have the Law to accuse him. He is condemned solely from the reasoning of nature, but the Jew the greater the attention he enjoyed, the greater the punishment he will suffer. For in that they said they did not need grace, being justified by the Law, he shows that they need it more than the Gentiles, considering they are liable to be punished more.