5 The laws of bondage, however, were one by one promulgated to the people by Moses, suited for their instruction or for their punishment, as Moses himself declared: “And the Lord commanded me at that time to teach you statutes and judgments.” These things, therefore, which were given for bondage, and for a sign to them, He cancelled by the new covenant of liberty. But He has increased and widened those laws which are natural, and noble, and common to all, granting to men largely and without grudging, by means of adoption, to know God the Father, and to love Him with the whole heart, and to follow His word unswervingly, while they abstain not only from evil deeds, but even from the desire after them.
But He has also increased the feeling of reverence; for sons should have more veneration than slaves, and greater love for their father. And therefore the Lord says, “As to every idle word that men have spoken, they shall render an account for it in the day of judgment.” And, “he who has looked upon a woman to lust after her, has committed adultery with her already in his heart;” and, “he that is angry with his brother without a cause, shall be in danger of the judgment.” [All this is declared,] that we may know that we shall give account to God not of deeds only, as slaves, but even of words and thoughts, as those who have truly received the power of liberty, in which [condition] a man is more severely tested, whether he will reverence, and fear, and love the Lord.
And for this reason Peter says “that we have not liberty as a cloak of maliciousness,” but as the means of testing and evidencing faith.
Source: Adversus haereses (New Advent)