in Romans 4:15 Paul says: for the law works wrath; but where there is no law, neither is there transgression.
In Romans 5:20 he repeats in similar words: And the law came in besides, that the trespass might abound; but where sin abounded, grace did abound more exceedingly.
Let me reiterate: in Romans 4:15: for the law works wrath; but where there is no law, neither is there transgression.
And in Romans 5:20: And the law came in besides, that the trespass might abound. The picture that he is giving is that the Law came in to cause more sin, to actually make us sin more.
How does that work? Paul explains it in Romans 7:7-13: What shall we say then? Is the law sin? God forbid. Howbeit, I had not known sin, except through the law: for I had not known coveting, except the law had said, You shall not covet: but sin, finding occasion, wrought in me through the commandment all manner of coveting: for apart from the law sin is dead. And I was alive apart from the law once: but when the commandment came, sin revived, and I died; and the commandment, which was unto life, this I found to be unto death: for sin, finding occasion, through the commandment beguiled me, and through it slew me. So that the law is holy, and the commandment holy, and righteous, and good. Did then that which is good become death unto me? God forbid. But sin, that it might be shown to be sin, by working death to me through that which is good;-that through the commandment sin might become exceeding sinful. Before I deal with this passage, let's read one more in I Corinthians 15:56: The sting of death is sin; and the power of sin is the law. Basically what Paul is saying in Romans 7 and I Corinthians 15 is that a sin-nature needs a base of operation; furthermore, the sin-nature uses the Law as a base of operation.
Paul said, “where there is no Law, there is no transgression.” He did not mean, of course, that there was not any sin before the Law was given. The term transgression is a specific type of sin in violation of a specific commandment. Men were sinners before the Law was given, but they were not transgressors of the Law until the Law was given.
Once the Law was given, then the sin-nature had a base of operation. Because as soon as the Law said “you shall not,” the sin-nature said, “oh yes I will.” Or as soon as the Law said, “you will do this,” the sin-nature said, “oh no I won't.” The sin-nature suddenly found a base of operation. The Law was used as a beachhead and suddenly all these new commandments were given, and the sin-nature “went to town” more or less, and started doing what it could to cause the individual to violate these commandments and sin all the more.