1 Now I shall simply say, in opposition to all the heretics, and principally against the followers of Marcion, and against those who are like to these, in maintaining that the prophets were from another God [than He who is announced in the Gospel], read with earnest care that Gospel which has been conveyed to us by the apostles, and read with earnest care the prophets, and you will find that the whole conduct, and all the doctrine, and all the sufferings of our Lord, were predicted through them.
But if a thought of this kind should then suggest itself to you, to say, What then did the Lord bring to us by His advent?— know that He brought all [possible] novelty, by bringing Himself who had been announced. For this very thing was proclaimed beforehand, that a novelty should come to renew and quicken mankind. For the advent of the King is previously announced by those servants who are sent [before Him], in order to the preparation and equipment of those men who are to entertain their Lord.
But when the King has actually come, and those who are His subjects have been filled with that joy which was proclaimed beforehand, and have attained to that liberty which He bestows, and share in the sight of Him, and have listened to His words, and have enjoyed the gifts which He confers, the question will not then be asked by any that are possessed of sense what new thing the King has brought beyond [that proclaimed by] those who announced His coming. For He has brought Himself, and has bestowed on men those good things which were announced beforehand, which things the angels desired to look into.
Source: Adversus haereses (New Advent)