Like many famous geniuses Origen sometimes went overboard in his ideas, like his speculation that maybe even the devil could be saved. That's why he never became a saint. But many of his ideas contributed a lot to the process of understanding the ramifications of the teachings of Jesus of Nazareth.
Today he discusses how the Old Testament showed that Jesus was the Messiah... and Jesus showed that the Old Testament was true.
But as it is not sufficient, in the discussion of matters of such importance, to entrust the decision to the human senses and to the human understanding, and to pronounce on things invisible as if they were seen by us, we must, in order to establish the positions which we have laid down, adduce the testimony of Holy Scripture. And that this testimony may produce a sure and unhesitating belief, either with regard to what we have still to advance, or to what has been already stated, it seems necessary to show, in the first place, that the Scriptures themselves are divine, i.e., were inspired by the Spirit of God.
We shall therefore with all possible brevity draw forth from the Holy Scriptures themselves, such evidence on this point as may produce upon us a suitable impression, (making our quotations) from Moses, the first legislator of the Hebrew nation, and from the words of Jesus Christ, the Author and Chief of the Christian religious system...
These points now being briefly established (that is regarding the deity of Christ, and the fulfillment of all that was prophesied respecting Him), I think that this position also has been made good: that the Scriptures themselves, which contained these predictions, were divinely inspired—those, namely, which had either foretold His advent, or the power of His doctrine, or the bringing over of all nations (to His obedience).
To which this remark must be added: that the divinity and inspiration both of the predictions of the prophets and of the law of Moses have been clearly revealed and confirmed, especially since the advent of Christ into the world. For before the fulfillment of those events which were predicted by them, they could not, although true and inspired by God, be shown to be so, because they were as yet unfulfilled. But the coming of Christ was a declaration that their statements were true and divinely inspired, although it was certainly doubtful before that whether there would be an accomplishment of those things which had been foretold.
Origen (AD 185 - 254)
(On First Principles, book 4 chapter 1 sections 1, 6)