Tertullian, Against Marcion 4

I still speak in human terms: when we were children, we were placed under the elemental forces of the world to serve them. Yet this is not a merely human saying, for it is not an illustration but the truth. What nation, in its childish understanding, is not subject to the world's elements, which it worships as gods? Still, the point I made in human terms stands: no one sets aside or overrides a human will. By appealing to the binding force of a human will, he safeguards the divine one: the promises were spoken to Abraham and to his seed. Scripture does not say 'seeds', implying many, but 'seed', referring to one, who is Christ (Gal 3:16). Let Marcion's sponge blush with shame! Unless, that is, I am now taking back what I previously conceded, since it is more damning to convict him from what he has kept. When the appointed time arrived, God sent his Son — the very one who is God of those ages that constitute the world, who set the celestial signs, the sun and moon, the stars and constellations, and who both arranged and foretold the revelation of his Son at the end of the ages: 'In the last days the mountain of the Lord will be revealed' (Isa 2:2), and 'In the last days I will pour out my Spirit on all flesh' (Joel 2:28). It belonged to him to sustain the era until its fulfillment, since the end of time was as much his as the beginning. But what did that idle God accomplish — a God with no action, no proclamation, and therefore no time of his own — to bring about the fullness of time and uphold it until it was due? If he did nothing, it is utterly vain that he, serving the Creator, should have sustained the Creator's times. To what purpose, then, did he send his Son? To redeem those under the law — that is, to make the crooked straight and the rough places smooth (Isa 40:3-5), so that the old order might pass and the new arise: a new law from Zion and the word of the Lord from Jerusalem (Isa 2:3) — and so that we might receive adoption as sons, we nations who were not sons. For he himself will be the light of the nations, and in his name the nations will hope (Isa 42:6; 49:6). Therefore, to make it certain that we are God's children, he sent his Spirit into our hearts crying, 'Abba, Father' (Rom 8:15). 'For in the last days,' he says, 'I will pour out my Spirit on all flesh' (Joel 2:28). Whose grace is this, if not his whose promise is also grace?