27 What can we say of men who in expounding the very Gospels so whittle away the human trust we should repose in it as to overturn Divine faith in it? They refuse to allow that the things which Christ said or did have come down to us unchanged and entire through witnesses who carefully committed to writing what they themselves had seen or heard. They maintain - and particularly in their treatment of the Fourth Gospel - that much is due of course to the Evangelists - who, however, added much from their own imaginations; but much, too, is due to narratives compiled by the faithful at other periods, the result, of course, being that the twin streams now flowing in the same channel cannot be distinguished from one another. Not thus did Jerome and Augustine and the other Doctors of the Church understand the historical trustworthiness of the Gospels; yet of it one wrote: "He who saw it has borne witness, and his witness is true; and he knows that he tells the truth, and you also may believe" ( Jn . 19:35). So, too, St. Jerome: after rebuking the heretical framers of the apocryphal Gospels for "attempting rather to fill up the story than to tell it truly," he says of the Canonical Scriptures: "None can doubt but that what is written took place." Here again he is in fullest harmony with Augustine, who so beautifully says: "These things are true; they are faithfully and truthfully written of Christ; so that whosoever believes His Gospel may be thereby instructed in the truth and misled by no lie."
Source: Spiritus Paraclitus (Vatican.va)