Tertullian, Against Marcion 11
Because 'god' has become a common term through the fault of human error — so much so that many gods are named and believed in throughout the world — the blessed God of our Lord Jesus Christ will nevertheless be understood as none other than the Creator. He both blessed all things (Genesis) and is blessed by all things (Daniel). Accordingly, if 'father' can be called a sterile god — with no name more fitting than the Creator's — the same one will still be the Father of mercies, who is declared merciful, a mercifier, and most full of mercies. You have Jonah as an example of his mercies, which he granted to the Ninevites when they prayed (Jonah); he was easily moved by Hezekiah's tears (2 Kings 20:1-6); he forgave the blood of Naboth when Ahab, the husband of Jezebel, pleaded for it (1 Kings 21:25-29); and he immediately granted indulgence to David when he acknowledged his fault (2 Samuel 12:13-14), plainly preferring the sinner's repentance to his death, out of the affection of mercy.
If Marcion's god has produced or promulgated anything of this kind, I will recognize the 'Father of mercies.' But if, on the other hand, he ascribes this title to him from the time he was revealed — as if from then on he is the Father of mercies — because he undertook to free the human race, then we deny him from that time, from which he is said to be revealed. For if it were previously established that he exists, then the title could also be ascribed to him; what is ascribed is an accident, and accidents presuppose the manifestation of the thing itself to which they happen. Therefore nothing can be ascribed to him whom he then shows, when he ascribes something to him — all the more since what is ascribed to him already belongs to another who was previously shown. To the extent that he affirms his existence through what belongs to that other, to that extent he will be denied existence.
Thus the 'new testament' will also belong to no one other than the one who promised it, even though its newness lies not in the letter but in the spirit. Finally, the one who inscribed the letter on stone tablets also promulgated the promise concerning the spirit: 'I will pour out my spirit on all flesh.' And if the letter kills while the spirit gives life, both are his, who says: 'I kill and I make alive; I wound and I heal.' We have formerly vindicated the Creator's double power — both as judge and as good — the letter killing through the law and the spirit giving life through the gospel.
Latin
Si 'deus' commune uocabulum factum est uitio erroris humani, quatenus plures dei dicuntur atque creduntur in saeculo, benedictus tamen deus domini nostri Iesu Christi non alius quam creator intellegetur, qui et uniuersa benedixit — habes Genesim — et ab uniuersis benedicitur — habes Danihelem —; proinde si 'pater* potest dici sterilis deus, [nullius magis nomine quam creatoris] misericordiarum tamen pater idem erit, qui misericors et miserator et misericordiae plurimus dictus est. habes apud Ionam cum ipso misericordiae exemplum, quam Niniuitis exorantibus praestitit, facilis et Ezechiae fletibus flecti, et Achab, marito Iezabel, deprecanti sanguinem ignoscere Nabuthae, et Dauid agnoscenti delictum statim indulgens, malens scilicet paenitentiam peccatoris quam mortem, utique ex misericordiae adfectu. si quid tale Marcionis deus edidit uel edixit, agnoscam 'patrem misericordiarum'. si uero ex eo tempore hunc titulum ei adscribit, quo reuelatus, quasi exinde sit (pater misericordiarum), quo liberare instituit genus humanum, atquin nos et ex eo tempore negamus illum, ex quo dicitur reuelatus. si enim prius constaret eum esse, tunc et adscribi ei posset. accidens enim est quod adscribitur, accidentia autem antecedit ipsius rei ostensio, cui accidunt. non potest igitur aliquid ei adscribere, quem tunc ostendit, cum aliquid ei adscribit; maxime cum iam alterius est quod adscribitur ei, qui prius non sit . ostensus. tanto (enim) magis negabitur esse, quanto per quod adfirmatur esse, eius est, qui iam ostensus est. Sic et 'testamentum nouum' non alterius erit quam qui illud repromisit, etsi non litterae at eius spiritus - hoc erit nouitas-, (is) denique, qui litteram tabulis lapideis inciderat, idem et de spiritu edixerat: effundam de meo spiritu in omnem carnem; et si litter a occidit, spiritus uero uiuificat, eius utrumque est, qui ait: ego occidam et ego uiuificabo, percutiam et sanabo. olim duplicem uim creatoris uindicauimus. et iudicis et boni, littera occidentis per legem et spiritu uiuificantis per euangelium.