Westminster Larger Catechism

Q. 95. Of what use is the moral law to all men?

A. The moral law is of use to all men, to inform them of the holy nature and will of God, and of their duty, binding them to walk accordingly; to convince them of their disability to keep it, and of the sinful pollution of their nature, hearts, and lives; to humble them in the sense of their sin and misery, and thereby help them to a clearer sight of the need they have of Christ, and of the perfection of his obedience.