His soul for our souls, His flesh for our flesh

Since the Lord thus has redeemed us through His own blood, giving His soul for our souls, and His flesh for our flesh, and has also poured out the Spirit of the Father for the union and communion of God and man, imparting indeed God to men by means of the Spirit, and, on the other hand, attaching man to God by His own incarnation, and bestowing upon us at His coming immortality durably and truly, by means of communion with God,—all the doctrines of the heretics fall to ruin.

Irenaeus of Lyons
Against Heresies, Book V
Chapter I

How can we be saved if Christ wasn’t God?

He will judge also the Ebionites; [for] how can they be saved unless it was God who wrought out their salvation upon earth? Or how shall man pass into God, unless God has [first] passed into man? And how shall he (man) escape from the generation subject to death, if not by means of a new generation, given in a wonderful and unexpected manner (but as a sign of salvation) by God—[I mean] that regeneration which flows from the virgin through faith?

Or how shall they receive adoption from God if they remain in this [kind of] generation, which is naturally possessed by man in this world? And how could He (Christ) have been greater than Solomon, or greater than Jonah, or have been the Lord of David, who was of the same substance as they were?

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XXXIII

 

God the Son became man to conquer the enemy

As I have pointed out in the preceding book, the apostle did, in the first place, instruct the Gentiles to depart from the superstition of idols, and to worship one God, the Creator of heaven and earth, and the Framer of the whole creation; and that His Son was His Word, by whom He founded all things; and that He, in the last times, was made a man among men; that He reformed the human race, but destroyed and conquered the enemy of man, and gave to His handiwork victory against the adversary.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XXI

The heretics rob humanity of promotion into God

To whom the Word says, mentioning His own gift of grace: “I said, Ye are all the sons of the Highest, and gods; but ye shall die like men.” He speaks undoubtedly these words to those who have not received the gift of adoption, but who despise the incarnation of the pure generation of the Word of God, defraud human nature of promotion into God, and prove themselves ungrateful to the Word of God, who became flesh for them. For it was for this end that the Word of God was made man, and He who was the Son of God became the Son of man, that man, having been taken into the Word, and receiving the adoption, might become the son of God. For by no other means could we have attained to incorruptibility and immortality, unless we had been united to incorruptibility and immortality. But how could we be joined to incorruptibility and immortality, unless, first, incorruptibility and immortality had become that which we also are, so that the corruptible might be swallowed up by incorruptibility, and the mortal by immortality, that we might receive the adoption of sons?

Irenaeus of Lyons
Against Heresies, Book III
Chapter XIX

 

Man becomes one with God by the Incarnation

For He is a most holy and merciful Lord, and loves the human race. Therefore, as I have already said, He caused man (human nature) to cleave to and to become, one with God. For unless man had overcome the enemy of man, the enemy would not have been legitimately vanquished. And again: unless it had been God who had freely given salvation, we could never have possessed it securely. And unless man had been joined to God, he could never have become a partaker of incorruptibility. 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?

Irenaeus of Lyons
Against Heresies, Book III
Chapter XVIII

Jesus, the first-born form the dead, existed before all

Then, at last, He came on to death itself, that He might be “the first-born from the dead, that in all things He might have the pre-eminence,” the Prince of life, existing before all, and going before all.

Irenaeus of Lyons
Against Heresies, Book II
Chapter XXII

God manifested in human form

Hence every kind of magic was destroyed, and every bond of wickedness disappeared; ignorance was removed, and the old kingdom abolished, God Himself being manifested in human form for the renewal of eternal life. And now that took a beginning which had been prepared by God. Henceforth all things were in a state of tumult, because He mediated the abolition of death.

Ignatius of Antioch
Epistle to the Ephesians
Chapter XIX

Jesus — the only true God

But our Physician is the only true God, the unbegotten and unapproachable, the Lord of all, the Father and Begetter of the only-begotten Son. We have also as a Physician the Lord our God, Jesus the Christ, the only-begotten Son and Word, before time began, but who afterwards became also man, of Mary the virgin. For “the Word was made flesh.” Being incorporeal, He was in the body; being impassible, He was in a passible body; being immortal, He was in a mortal body; being life, He became subject to corruption, that He might free our souls from death and corruption, and heal them, and might restore them to health, when they were diseased with ungodliness and wicked lusts.

Ignatius of Antioch
Epistle to the Ephesians
Chapter VII

Jesus is our exchange

By what other one was it possible that we, the wicked and ungodly, could be justified, than by the only Son of God? O sweet exchange! O unsearchable operation! O benefits surpassing all expectation! That the wickedness of many should be hid in a single righteous One, and that the righteousness of One should justify many transgressors!

Mathetes
Epistle to Diognetus
Chapter IX