It were indeed meet for us not at all to require the aid of the written Word, but to exhibit a life so pure, that the grace of the Spirit should be instead of books to our souls, and that as these are inscribed with ink, even so should our hearts be with the Spirit. But, since we have utterly put away from us this grace, come, let us at any rate embrace the second best course.
For that the former was better, God has made manifest, both by His words, and by His doings. Since unto Noah, and unto Abraham, and unto his offspring, and unto Job, and unto Moses too, He discoursed not by writings, but Himself by Himself, finding their mind pure. But after the whole people of the Hebrews had fallen into the very pit of wickedness, then and thereafter was a written word, and tables, and the admonition which is given by these.
And this one may perceive was the case, not of the saints in the Old Testament only, but also of those in the New. For neither to the apostles did God give anything in writing, but instead of written words He promised that He would give them the grace of the Spirit: for “He,” says our Lord, “shall bring all things to your remembrance.” And that you may learn that this was far better, hear what He says by the Prophet: “I will make a new covenant with you, putting my laws into their mind, and in their heart I will write them,” and, “they shall be all taught of God.” And Paul too, pointing out the same superiority, said, that they had received a law “not in tables of stone, but in fleshy tables of the heart.”
But since in process of time they made shipwreck, some with regard to doctrines, others as to life and manners, there was again need that they should be put in remembrance by the written word.
Source: Homilies on the Gospel of St. Matthew (New Advent)