(Vs. 12) Divine justice will deal with sin; in whomsoever sin is found, he shall perish! The Gentiles who have not the written Law of Moses shall perish, for they have sinned against the light of nature, conscience, and the law written on their hearts. On the other hand the Jews, who have the written Law, shall be judged by that Law and condemned. Their having the Law, hearing the Law, or partially doing the Law shall not free them from condemnation, but rather shall increase their misery.
Two objections are generally raised against these words: (1) since God has not given the written Law to the heathen, they ought not be condemned; and (2) since God gave the Jews His written Law and declared them to be a special people, they should be spared. Both of these are dealt with in the next three verses enclosed by a parenthesis.
(Vs. 13) Reading the Law, preaching the Law, and hearing the Law may justify a man in his own eyes and even in the eyes of men; but it will not justify him before God (Luke 16:15; Matt. 23:27-28). If a man would seek righteousness from or by the Law, it must be a perfect inward and outward obedience (Gal. 4:21; Gal. 3:10). The commandments of God are not given for consideration, curiosity, or contemplation but to be perfectly obeyed. Without a perfect holiness, no man shall be justified (Matt. 5:20). This righteousness is ours in Christ (Rom. 3:19-26) through faith.
(Vs. 14) This verse supplies the answer to the objection that God cannot justly condemn the heathen since He has given them no written Law. Paul states that though they have not a written Law, they have proven by their own deeds that they have a law in themselves, put there by God. The heathen does certain things (though imperfectly) commanded by the Law, which proves they discern the difference between right and wrong.
(Vs. 15) Haldane distinguishes between the Law itself and the WORK of the Law. The work of the Law is the thing that the Law does; that is, what it teaches about good and bad, right and wrong. The Gentiles, who institute religious rites, make laws to punish theft, murder, and adultery, and reward honesty and truth, prove that there is imprinted on their hearts the work of the Law, which distinguishes between what is just and unjust. The testimony of their own conscience witnesses against them.
"They accuse or excuse one another." This supposes a knowledge of right and wrong. No man can accuse or condemn another if he has no standard of right and wrong, and no man can defend an action unless he has a similar standard. The Gentile is not without law, though he is without the written Law of Moses; and he shall be judged and condemned according to light and knowledge (Rom. 1:18-20).
(Vs. 16) These words are to be read in connection with verse 13. They express the time when both Jews and Gentiles shall be judged. As there is LAW common to the whole human race, there is a common JUDGE, Who is God; and there will be a DAY when God will hold this judgment (Rev. 20:12-15; I Cor. 4:5).
"The secrets of men" means that this judgment will include all things, even the most secret and most concealed. It is not like the judgments of men which cannot discern the thoughts and the heart. God will not only expose the external but the internal guilt, even the inmost thoughts of men (Eccles. 12:14).
"By Jesus Christ." Jesus Christ will conduct the judgment, for He is the Judge of the quick and the dead; and to Him hath the Father committed all things (John 5:22; Acts 17:31; Rev. 1:17-18).
"According to my gospel." That is, the gospel which he preached. The gospel includes everything revealed by Christ, and this judgment is declared therein (Mark 16:15-16; John 3:18, 36).
"In the economy of Jesus Christ there are two extreme degrees, one of abasement, the other of exaltation. The lowest degree of His abasement was His death and burial. The opposite degree of His exaltation will be the last Judgment. In His death He was covered with reproaches and pierced with the arrows of Divine justice. He was exposed on the cross as a spectacle to the whole city of Jerusalem. In the Last Judgment, arrayed in glory and majesty, He will appear before the whole universe in the glory of His Father (Phil. 2:6-11)." –Robert Haldane