Irenaeus

For it was incumbent upon the Mediator between God and men, by His relationship to both, to bring both to friendship and concord, and present man to God, while He revealed God to man. For, in what way could we be partaken of the adoption of sons, unless we had received from Him through the Son that fellowship which refers to Himself, unless His Word, having been made flesh, had entered into communion with us? Wherefore also He passed through every stage of life, restoring to all communion with God. Those, therefore, who assert that He appeared putatively, and was neither born in the flesh nor truly made man, are as yet under the old condemnation, holding out patronage to sin; for, by their showing, death has not been vanquished, which "reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression."

But the law coming, which was given by Moses, and testifying of sin that it is a sinner, did truly take away his (death's) kingdom, showing that he was no king, but a robber; and it revealed him as a murderer. It laid, however, a weighty burden upon man, who had sin in himself, showing that he was liable to death. For as the law was spiritual, it merely made sin to stand out in relief, but did not destroy it. For sin had no dominion over the spirit, but over man. For it behoved Him who was to destroy sin, and redeem man under the power of death, that He should Himself be made that very same thing which he was, that is, man; who had been drawn by sin into bondage, but was held by death, so that sin should be destroyed by man, and man should go forth from death.

Wherefore Luke points out that the pedigree which traces the generation of our Lord back to Adam contains seventy-two generations, connecting the end with the beginning, and implying that it is He who has summed up in Himself all nations dispersed from Adam downwards, and all languages and generations of men, together with Adam himself. Hence also was Adam himself termed by Paul "the figure of Him that was to come," because the Word, the Maker of all things, had formed beforehand for Himself the future dispensation of the human race, connected with the Son of God; God having predestined that the first man should be of an animal nature, with this view, that he might be saved by the spiritual One. For inasmuch as He had a pre-existence as a saving Being, it was necessary that what might be saved should also be called into existence, in order that the Being who saves should not exist in vain.