1 Timothy 1:9

1 Tim. 1:9. "Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers." This may be given as a reason why the precepts of the moral Law were not expressed by God to our [first] parents as well as that positive precept of not eating the forbidden fruit. There is not that need of God expressly and particularly forbidding these and other immoralities to one that is perfectly righteous in his nature, either for the making known his obligation, or for the enforcing it, as to one that is of corrupt nature.

God, in His infinite wisdom, never would have seen cause expressly to reveal the moral Law had it not been for transgressions, or man's disposition to sin.