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

Man’s free will is involved in repentence

Foolish heretic, who treat with scorn so fine an argument of God’s greatness and man’s instruction! God put the question with an appearance of uncertainty, in order that even here He might prove man to be the subject of a free will in the alternative of either a denial or a confession, and give to him the opportunity of freely acknowledging his transgression, and, so far, of lightening it.

Tertullian
The Five Books Against Marcion, Book II
Chapter XXV

God will judge our works

Now, who is so faultless among men, that God could always have him in His choice, and never be able to reject him? Or who, on the other hand, is so void of any good work, that God could reject him for ever, and never be able to choose him? Show me, then, the man who is always good, and he will not be rejected; show me, too, him who is always evil, and he will never be chosen.  Should, however, the same man, being found on different occasions in the pursuit of both (good and evil) be recompensed in both directions by God, who is both a good and judicial Being, He does not change His judgments through inconstancy or want of foresight, but dispenses reward according to the deserts of each case with a most unwavering and provident decision.

Tertullian
The Five Books Against Marcion, Book II
Chapter XXIII

Christians believe God became man and died

We who believe that God really lived on earth, and took upon Him the low estate of human form, for the purpose of man’s salvation, are very far from thinking as those do who refuse to believe that God cares for anything.

…Fortunately, however, it is a part of the creed of Christians even to believe that God did die, and yet that He is alive for evermore.

Tertullian
The Five Books Against Marcion, Book II
Chapter XVI

Justice is the fullness of the Deity himself

Thus the entire office of justice in this respect becomes an agency for goodness: whatever it condemns by its judgment, whatever it chastises by its condemnation, whatever (to use your phrase) it ruthlessly pursues, it, in fact, benefits with good instead of injuring. Indeed, the fear of judgment contributes to good, not to evil. For good, now contending with an enemy, was not strong enough to recommend itself by itself alone.

…We dread the Creator’s tremendous threats, and yet scarcely turn away from evil. What, if He threatened not? Will you call this justice an evil, when it is all unfavourable to evil? Will you deny it to be a good, when it has its eye towards good? What sort of being ought you to wish God to be? Would it be right to prefer that He should be such, that sins might flourish under Him, and the devil make mock at Him? Would you suppose Him to be a good God, who should be able to make a man worse by security in sin? Who is the author of good, but He who also requires it? In like manner who is a stranger to evil, except Him who is its enemy? Who its enemy, besides Him who is its conqueror? Who else its conqueror, than He who is its punisher? Thus God is wholly good, because in all things He is on the side of good.

…How can I follow after the reward of innocence, if I have no regard to the requital of wrong-doing?

…Thus far, then, justice is the very fulness of the Deity Himself, manifesting God as both a perfect father and a perfect master: a father in His mercy, a master in His discipline; a father in the mildness of His power, a master in its severity; a father who must be loved with dutiful affection, a master who must needs be feared; be loved, because He prefers mercy to sacrifice; be feared because He dislikes sin; be loved, because He prefers the sinner’s repentance to his death; be feared, because He dislikes the sinners who do not repent.

Accordingly, the divine law enjoins duties in respect of both these attributes: Thou shalt love God, and, Thou shalt fear God. It proposed one for the obedient man, the other for the transgressor.

Tertullian
The Five Books Against Marcion, Book II
Chapter XIII

Justice is an evil if God is not considered a judge

You should now set about showing also that the position of a judge is allied with evil, who have been dreaming of another god as a purely good one—solely because you cannot understand the Deity to be a judge; although we have proved God to be also a judge. Or if not a judge, at any rate a perverse and useless originator of a discipline which is not to be vindicated—in other words, not to be judged.  You do not, however, disprove God’s being a judge, who have no proof to show that He is a judge. You will undoubtedly have to accuse justice herself, which provides the judge, or else to reckon her among the species of evil, that is, to add injustice to the titles of goodness. But then justice is an evil, if injustice is a good.

goodness (unless justice be so controlled as to be just) will not be goodness, if it be unjust. For nothing is good which is unjust; while everything, on the other hand, which is just is good.

Tertullian
The Five Books Against Marcion, Book II
Chapter XI

The Spirit of God is God

We must at the outset hold fast the meaning of the Greek scripture, which has afflatus, not spirit. Some interpreters of the Greek, without reflecting on the difference of the words, and careless about their exact meaning, put spirit for afflatus; they thus afford to heretics an opportunity of tarnishing the Spirit of God, that is to say, God Himself, with default.

Tertullian
The Five Books Against Marcion, Book II
Chapter IX

Our free will plays a part in our salvation

And thus it comes to pass, that even now also, the same human being, the same substance of his soul, the same condition as Adam’s, is made conqueror over the same devil by the self-same liberty and power of his will, when it moves in obedience to the laws of God.

Tertullian
The Five Books Against Marcion, Book II
Chapter VIII