God was born

Come then, wind up your cavils against the most sacred and reverend works of nature; inveigh against all that you are; destroy the origin of flesh and life; call the womb a sewer of the illustrious animal—in other words, the manufactory for the production of man; dilate on the impure and shameful tortures of parturition, and then on the filthy, troublesome, contemptible issues of the puerperal labour itself! But yet, after you have pulled all these things down to infamy, that you may affirm them to be unworthy of God, birth will not be worse for Him than death, infancy than the cross, punishment than nature, condemnation than the flesh. If Christ truly suffered all this, to be born was a less thing for Him. If Christ suffered evasively, as a phantom; evasively, too, might He have been born. Such are Marcion’s chief arguments by which he makes out another Christ; and I think that we show plainly enough that they are utterly irrelevant, when we teach how much more truly consistent with God is the reality rather than the falsehood of that condition in which He manifested His Christ. Since He was “the truth,” He was flesh; since He was flesh, He was born.

Tertullian
The Five Books Against Marcion, Book III
Chapter XI

The flesh became a vestment for God himself

But yet, if we look steadily into the subject, there is really no substance which is worthy of becoming a vestment for God. Whatsoever He is pleased to clothe Himself withal, He makes worthy of Himself—only without untruth. Therefore how comes it to pass that he should have thought the verity of the flesh, rather than its unreality, a disgrace?

Tertullian
The Five Books Against Marcion, Book III
Chapter X

Christ regenerated our lives through incarnation and resurrection

…none but Christ could become incarnate by being born of the flesh in order that by His own nativity He might regenerate our birth, and might further by His death also dissolve our death, by rising again in that flesh in which, that He might even die, He was born.

Tertullian
The Five Books Against Marcion, Book III
Chapter IX

Christ and the Spirit are one substance with the Creator

For when you do not deny that the Creator’s Son and Spirit and Substance is also His Christ, you must needs allow that those who have not acknowledged the Father have failed likewise to acknowledge the Son through the identity of their natural substance; for if in Its fulness It has baffled man’s understanding, much more has a portion of It, especially when partaking of the fulness.

Tertullian
The Five Books Against Marcion, Book III
Chapter VI

God became man so man might learn to act as god

God held converse with man, that man might learn to act as God. God dealt on equal terms with man, that man might be able to deal on equal terms with God. God was found little, that man might become very great. You who disdain such a God, I hardly know whether you ex fide believe that God was crucified.

Tertullian
The Five Books Against Marcion, Book II
Chapter XXVIII

Christ, as a human being, is our God

Now we believe that Christ did ever act in the name of God the Father; that He actually from the beginning held intercourse with (men); actually communed with patriarchs and prophets; was the Son of the Creator; was His Word; whom God made His Son by emitting Him from His own self, and thenceforth set Him over every dispensation and (administration of) His will, making Him a little lower than the angels, as is written in David.

…For even in the Old Testament He had declared, “No man shall see me, and live.” He means that the Father is invisible, in whose authority and in whose name was He God who appeared as the Son of God. But with us Christ is received in the person of Christ, because even in this manner is He our God.

Tertullian
The Five Books Against Marcion, Book II
Chapter XXVII

God moved about in human form

Inasmuch as ye yourselves have now come to the belief that God moved about in the form and all other circumstances of man’s nature, you will of course no longer require to be convinced that God conformed Himself to humanity, but feel yourselves bound by your own faith. For if the God (in whom ye believe,) even from His higher condition, prostrated the supreme dignity of His majesty to such a lowliness as to undergo death, even the death of the cross, why can you not suppose that some humiliations are becoming to our God also, only more tolerable than Jewish contumelies, and crosses, and sepulchres?

Tertullian
The Five Books Against Marcion, Book II
Chapter XXVII