Tertullian, Against Marcion 4

The apostle adds that he is still speaking in human terms: while we were mere children, we were placed under the elemental spirits of the world to serve them. Yet this is no mere human illustration; it is the truth itself. For what child — certainly in understanding, since the nations are such children — is not subject to the world's elemental spirits, which they worship as gods? That statement was made 'according to man' at that time; even so, no one sets aside or adds to 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', as if referring to many, but 'seed', as if one — and that one is Christ (Gal 3:16). Let Marcion's erasing sponge be ashamed! Unless I am simply drawing out what he deleted, since it is even more damning to convict him from the very texts he preserved.

When the fullness of time arrived, God sent his Son — the very one who is also God of those times that constitute the age, who ordained the signs of the times, sun and moon and stars, 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 manifest' (Isa 2:2-3), and 'In the last days I will pour out my Spirit upon all flesh,' according to Joel (Joel 2:28-29). It belonged to him to sustain the fullness of time, since the end of time was his no less than its beginning. What, then, did that idle god accomplish — a god with no operation, no prediction, and therefore no time of his own — to bring about the fullness of time and sustain it now that it is being fulfilled? If nothing, it is utterly vain that he, serving the Creator, merely sustained the Creator's times.

To what end did he send his Son? To redeem those who were under the law — that is, to make the crooked straight and the rough places smooth, according to Isaiah (Isa 40:3-4), so that the old order might pass away and the new arise: 'A new law from Zion, and the word of the Lord from Jerusalem' — 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 the nations will hope in his name (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' (Gal 4:6). 'For in the last days,' he says, 'I will pour out my Spirit upon all flesh' (Joel 2:28-29). Whose grace is this, if not his, whose is also the promise of grace?