The Doctrine of the Truth Continued
This Logos the Father in the latter days sent forth, no longer to speak by a prophet, and not wishing that the Word, being obscurely proclaimed, should be made the subject of mere conjecture, but that He should be manifested, so that we could see Him with our own eyes. This Logos, I say, the Father sent forth, in order that the world, on beholding Him, might reverence Him who was delivering precepts not by the person of prophets, nor terrifying the soul by an angel, but who was Himself— He that had spoken— corporally present among us.
This Logos we know to have received a body from a virgin, and to have remodelled the old man by a new creation. And we believe the Logos to have passed through every period in this life, in order that He Himself might serve as a law for every age, and that, by being present (among) us, He might exhibit His own manhood as an aim for all men. And that by Himself in person He might prove that God made nothing evil, and that man possesses the capacity of self-determination, inasmuch as he is able to will and not to will, and is endued with power to do both. This Man we know to have been made out of the compound of our humanity.
For if He were not of the same nature with ourselves, in vain does He ordain that we should imitate the Teacher. For if that Man happened to be of a different substance from us, why does He lay injunctions similar to those He has received on myself, who am born weak; and how is this the act of one that is good and just? In order, however, that He might not be supposed to be different from us, He even underwent toil, and was willing to endure hunger, and did not refuse to feel thirst, and sunk into the quietude of slumber.
He did not protest against His Passion, but became obedient unto death, and manifested His resurrection. Now in all these acts He offered up, as the first-fruits, His own manhood, in order that you, when you are in tribulation, may not be disheartened, but, confessing yourself to be a man (of like nature with the Redeemer), may dwell in expectation of also receiving what the Father has granted unto this Son.
Source: The Refutation of All Heresies (New Advent)