Romans 5:20-21

Now the law entered in. Not that the law was designed for that end; but the word that, as in many other places, so here expresseth only the consequence that followed, when sinners occasionally became more guilty by the knowledge of the law, and the precepts given. St. John Chrysostom takes notice that it is not said the law was given, but only that it entered in, as it were by the by, and only for a certain time, till our happy redemption, reconciliation, and justification by Jesus Christ. (Witham) --- That sin might abound. Not as if the law were given purposely for sin to abound; but that it so happened, through man's perversity, taking occasion of sinning more, from the prohibition of sin. (Challoner) --- Where sin abounded. Grace abounded in the elect; for the apostle does not say that grace abounded in every place where sin abounded; but he says indefinitely where, that is, in many places where sin abounded, grace hath abounded also. (Estius) --- The Jews and Gentiles having become sensible of their weakness and misery, the Almighty, in his mercy, sent his only Son to enrich both the one and the other with his graces. The Gentiles were in the more deplorable case, and received the greatest abundance of grace; as may be seen from the great number of conversion wrought amongst them in so short a time in every part of the world. (Calmet) --- In the Greek it is Greek: pareiselthe, entered in by stealth, as it were, and for a time, till the preaching of the gospel. (Menochius)