Christ is God and comes from within God as the first begotten

The sacred books acknowledge with regard to Christ, that as He is the Son of man, so is the same Being not a [mere] man; and as He is flesh, so is He also spirit, and the Word of God, and God. And as He was born of Mary in the last times, so did He also proceed from God as the First-begotten of every creature; and as He hungered, so did He satisfy [others]; and as He thirsted, so did He of old cause the Jews to drink, for the “Rock was Christ” Himself: thus does Jesus now give to His believing people power to drink spiritual waters, which spring up to life eternal.

…And as He was the servant of God, so is He the Son of God, and Lord of the universe.

Irenaeus of Lyons
Lost Writings
Fragment LII

Christ’s body as the Ark of the Covenant

For as the ark [of the covenant] was gilded within and without with pure gold, so was also the body of Christ pure and resplendent; for it was adorned within by the Word, and shielded without by the Spirit, in order that from both [materials] the splendor of the natures might be clearly shown forth.

…so is that ark declared a type of the body of Christ, which is both pure and immaculate.

Irenaeus of Lyons
Lost Writings
Fragment VIII and XLVIII

Through the “person” of the Spirit we see

These things, therefore, He recapitulated in Himself: by uniting man to the Spirit, and causing the Spirit to dwell in man, He is Himself made the head of the Spirit, and gives the Spirit to be the head of man: for through Him (the Spirit) we see, and hear, and speak.

Irenaeus of Lyons
Against Heresies, Book V
Chapter XX

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

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 separate Christ from the Father as two different Gods

These things did the prophets set forth in a prophetical manner; but they did not, as some allege, [proclaim] that He who was seen by the prophets was a different [God], the Father of all being invisible. Yet this is what those [heretics] declare, who are altogether ignorant of the nature of prophecy.

…The prophets, then, indicated beforehand that God should be seen by men; as the Lord also says, “Blessed are the pure in heart, for they shall see God.”

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XX

Christ joins man to God through the incarnation

Now this is His Word, our Lord Jesus Christ, who in the last times was made a man among men, that He might join the end to the beginning, that is, man to God. Wherefore the prophets, receiving the prophetic gift from the same Word, announced His advent according to the flesh, by which the blending and communion of God and man took place according to the good pleasure of the Father, the Word of God foretelling from the beginning that God should be seen by men, and hold converse with them upon earth, should confer with them, and should be present with His own creation, saving it, and becoming capable of being perceived by it, and freeing us from the hands of all that hate us, that is, from every spirit of wickedness; and causing us to serve Him in holiness and righteousness all our days, in order that man, having embraced the Spirit of God, might pass into the glory of the Father.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter XX

The Father made His Word visible

And for this purpose did the Father reveal the Son, that through His instrumentality He might be manifested to all, and might receive those righteous ones who believe in Him into incorruption and everlasting enjoyment (now, to believe in Him is to do His will); but He shall righteously shut out into the darkness which they have chosen for themselves, those who do not believe, and who do consequently avoid His light. The Father therefore has revealed Himself to all, by making His Word visible to all; and, conversely, the Word has declared to all the Father and the Son, since He has become visible to all. And therefore the righteous judgment of God [shall fall] upon all who, like others, have seen, but have not, like others, believed.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter VI

The virgin birth was unexpected

For what great thing or what sign should have been in this, that a young woman conceiving by a man should bring forth,—a thing which happens to all women that produce offspring? But since an unlooked-for salvation was to be provided for men through the help of God, so also was the unlooked-for birth from a virgin accomplished; God giving this sign, but man not working it out. On this account

Irenaeus of Lyons
Against Heresies, Book III
Chapter XXI