Christ spoke through the prophets and they named Him God

But by the law and the prophets did the Word preach both Himself and the Father alike [to all]; and all the people heard Him alike, but all did not alike believe. And through the Word Himself who had been made visible and palpable, was the Father shown forth, although all did not equally believe in Him; but all saw the Father in the Son: for the Father is the invisible of the Son, but the Son the visible of the Father. And for this reason all spake with Christ when He was present [upon earth], and they named Him God.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter VI

The Father and the Word are Creator

For by means of the creation itself, the Word reveals God the Creator; and by means of the world [does He declare] the Lord the Maker of the world; and by means of the formation [of man] the Artificer who formed him; and by the Son that Father who begat the Son: and these things do indeed address all men in the same manner, but all do not in the same way believe them.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter VI

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

Irenaeus quotes Justin Martyr against Marcion

In his book against Marcion, Justin does well say: “I would not have believed the Lord Himself, if He had announced any other than He who is our framer, maker, and nourisher. But because the only-begotten Son came to us from the one God, who both made this world and formed us, and contains and administers all things, summing up His own handiwork in Himself, my faith towards Him is stedfast, and my love to the Father immoveable, God bestowing both upon us.”

Irenaeus of Lyons
Against Heresies, Book IV
Chapter VI

He is God and man, as prophesied in Isaiah

Carefully, then, has the Holy Ghost pointed out, by what has been said, His birth from a virgin, and His essence, that He is God (for the name Emmanuel indicates this). And He shows that He is a man, when He says, “Butter and honey shall He eat;” and in that He terms Him a child also, [in saying,] “before He knows good and evil;” for these are all the tokens of a human infant. But that He “will not consent to evil, that He may choose that which is good,”—this is proper to God; that by the fact, that He shall eat butter and honey, we should not understand that He is a mere man only, nor, on the other hand, from the name Emmanuel, should suspect Him to be God without flesh.

Irenaeus of Lyons
Against Heresies, Book III
Chapter XXI

The Son of God, who is God, came from Judah

And that it is from that region which is towards the south of the inheritance of Judah that the Son of God shall come, who is God, and who was from Bethlehem, where the Lord was born [and] will send out His praise through all the earth…

…Thus he indicates in clear terms that He is God, and that His advent was [to take place] in Bethlehem, and from Mount Effrem which is towards the south of the inheritance, and that [He is] man.

Irenaeus of Lyons
Against Heresies, Book III
Chapter XX

Christ is beyond all men who ever lived, God and Lord

He who “was not born either by the will of the flesh, or by the will of man,” is the Son of man, this is Christ, the Son of the living God. For I have shown from the Scriptures, that no one of the sons of Adam is as to everything, and absolutely, called God, or named Lord. But that He is Himself in His own right, beyond all men who ever lived, God, and Lord, and King Eternal, and the Incarnate Word, proclaimed by all the prophets, the apostles, and by the Spirit Himself, may be seen by all who have attained to even a small portion of the truth. Now,

Irenaeus of Lyons
Against Heresies, Book III
Chapter XIX