John Chrysostom : Then John bears witness to this: "When John had first preached before His coming the baptism of repentance to all the people of Israel. And as John fulfilled his course, he said, Whom think ye that I am? I am not He. But, behold, there cometh one after me, whose shoes of His feet I am not worthy to loose." And John too not merely bears witness to the fact, but does it in such sort that when men were bringing the glory to him, he declines it: for it is one thing not to affect an honor which nobody thinks of offering; and another, to reject it when all men are ready to give it, and not only to reject it, but to do so with such humility. Then he adduces John: then again the prophets, where he says, "By condemning they fulfilled," and again, "All that was written:" then the Apostles as witnesses of the Resurrection: then David bearing witness. For neither the Old Testament proofs seemed so cogent when taken by themselves as they are in this way, nor yet the latter testimonies apart from the former: wherefore he makes them mutually confirm each other. "Of this man's seed," etc. "When John," he says, "had first preached before His entry" - by entry he means the Incarnation - "the baptism of repentance to all the people of Israel." Thus also John, writing his Gospel, continually has recourse to him: for his name was much thought of in all parts of the world. And observe, he does not say it "Of this man's seed," etc. from himself, but brings John's testimony. — Homily on Acts 29 Origen of Alexandria : It must be said, on the one hand, that the Old [Testament] is not a Gospel since it did not show "the one coming" but announced him beforehand, and on the other that the entire New [Testament] is the gospel, speaking not just in a way similar to the beginning of the Gospel, "Behold, the lamb of God that takes away the sin of the world," but encompassing manifold praises and teachings of the one on whose account the Gospel is the gospel. — COMMENTARY ON THE GOSPEL OF John 1.17