Adam Clarke on Romans 2:13

For not the hearers of the law, etc. - It does not follow, because one people are favored with a Divine revelation, that therefore they shall be saved; while the others who have not had that revelation, shall finally perish: this is not God's procedure; where he has given a law - a Divine revelation, he requires obedience to that law; and only those who have been doers of that law - who have lived according to the light and privileges granted in that revelation, shall be justified - shall be finally acknowledged to be such as are fit for the kingdom of God.