Augustine of Hippo, Against Two Letters of the Pelagians III.3: Scriptural Confirmation of the Catholic Doctrine

This is what we say; this is that about which they object to us that we say “that the law was so given as to be a cause of greater sin.” They do not hear the apostle saying, “For the law worketh wrath; for where no law is, there is no transgression;” and, “The law was added for the sake of transgression until the seed should come to whom the promise was made;” and, “If there had been a law given which could have given life, righteousness should altogether have been by the law; but the Scripture hath concluded all under sin, that the promise by faith of Jesus Christ might be given to them that believe.” Hence it is that the Old Testament, from the Mount Sinai, where the law was given, gendereth to bondage, which is Agar. “Now we,” says he, “are not children of the bondmaid but of the freewoman.” Therefore they are not children of the freewoman who have accepted the law of the letter, whereby they can be shown to be not only sinners, but moreover transgressors; but they who have received the Spirit of grace, whereby the law itself, holy and just and good, may be fulfilled. This is what we say: let them attend and not contend; let them seek enlightenment and not bring false accusations.