Ante-Nicene Fathers, Vol III:
Tertullian: Part II: Marcion, Justifying His Antithesis Between the Law and the Gospel by the Contention of St. Paul with St. Peter, Shown to Have Mistaken St. Paul's Position and Argument.  Marcion's Doctrine Confuted Out of St. Paul's Teaching, Which Agrees Wholly with the Creator's Decrees.

Chapter XX.—Marcion, Justifying His Antithesis Between the Law and the Gospel by the Contention of St. Paul with St. Peter, Shown to Have Mistaken St. Paul’s Position and Argument. Marcion’s Doctrine Confuted Out of St. Paul’s Teaching, Which Agrees Wholly with the Creator’s Decrees.

This most patent conclusion requires to be defended by us against the clamours of the opposite side. For they allege that Marcion did not so much innovate on the rule (of faith) by his separation of the law and the gospel, as restore it after it had been previously adulterated. O Christ, 2553 most enduring Lord, who didst bear so many years with this interference with Thy revelation, until Marcion forsooth came to Thy rescue! Now they adduce the case of Peter himself, and the others, who were pillars of the apostolate, as having been blamed by Paul for not walking uprightly, according to the truth of the gospel—that very Paul indeed, who, being yet in the mere rudiments of grace, and trembling, in short, lest he should have run or were still running in vain, then for the first time held intercourse with those who were apostles before himself. Therefore because, in the eagerness of his zeal against Judaism as a neophyte, he thought that there was something to be blamed in their conduct—even the promiscuousness of their conversation 2554 —but afterwards was himself to become in his practice all things to all men, that he might gain all,—to the Jews, as a Jew, and to them that were under the law, as under the law,—you would have his censure, which was merely directed against conduct destined to become acceptable even to their accuser, suspected of prevarication against God on a point of public doctrine. 2555 Touching their public doctrine, however, they had, as we have already said, joined hands in perfect concord, and had agreed also in the division of their labour in their fellowship of the gospel, as they had indeed in all other respects: 2556 “Whether it were I or they, so we preach.” 2557 When, again, he mentioned “certain false brethren as having crept in unawares,” who wished to remove the Galatians into another gospel, 2558 he himself shows that that adulteration of the gospel was not meant to transfer them to the faith of another god and christ, but rather to perpetuate the teaching of the law; because he blames them for maintaining circumcision, and observing times, and days, and months, and years, according to those Jewish ceremonies which they ought to have known were now abrogated, according to the new dispensation purposed by the Creator Himself, who of old foretold this very thing by His prophets. Thus He says by Isaiah: Old things have passed away. “Behold, I will do a new thing.” 2559 And in another passage: “I will make a new covenant, not according to the covenant that I made with their fathers, when I brought them out of the land of p. 286 Egypt.” 2560 In like manner by Jeremiah: Make to yourselves a new covenant, “circumcise yourselves to the Lord, and take away the foreskins of your heart.” 2561 It is this circumcision, therefore, and this renewal, which the apostle insisted on, when he forbade those ancient ceremonies concerning which their very founder announced that they were one day to cease; thus by Hosea: “I will also cause all her mirth to cease, her feast-days, her new moons, and her Sabbaths, and all her solemn feasts.” 2562 So likewise by Isaiah: “The new moons, and Sabbaths, the calling of assemblies, I cannot away with; your holy days, and fasts, and feast-days, my soul hateth.” 2563 Now, if even the Creator had so long before discarded all these things, and the apostle was now proclaiming them to be worthy of renunciation, the very agreement of the apostle’s meaning with the decrees of the Creator proves that none other God was preached by the apostle than He whose purposes he now wished to have recognised, branding as false both apostles and brethren, for the express reason that they were pushing back the gospel of Christ the Creator from the new condition which the Creator had foretold, to the old one which He had discarded.

Footnotes

Tertullian’s indignant reply.

Passivum scilicet convictum.

Prædicationis. [Largely ad hominem, this argument.]

Et alibi.

1 Cor. xv. 11.

See Gal. 1:6, 7, Gal. 2:4.

Isa. xliii. 19.

This quotation, however, is from Jer. xxxi. 32.

Jer. iv. 4.

Hos. ii. 11.

Slightly altered from Isa. 1:13, 14.