They are both indeed found in a passage (Adv.Haer.i.

20.
2, 3) where Irenaeus is quoting the heretical Marcosians; and various approximations are met with, as we have seen, under ambiguous circumstances in Justin, the Clementine Homilies, and Marcion.

But similar approximations are also found in Irenaeus himself (speaking in his own person), in Clement of Alexandria, Origen, and Epiphanius, who are undoubtedly quoting from our Gospels; so that the presence of the variations at that early date is proved, though in the first case they receive none, and in the second very limited, support from the extant MSS.

[Endnote 332:1] A variety of reading that was in the first instance accidental seemed to afford a handle either to the orthodox or to heretical parties, and each for a time maintained its own; but with the victory of the orthodox cause the heretical reading gave way, and was finally suppressed before the time at which the extant MSS.
were written.
These are really conspicuous instances of the confusion of text already existing, but I forbear to press them because, though I do not doubt myself the correctness of the account that has been given of them, still there is just the ambiguity alluded to, and I do not wish to seem to assume the truth of any particular view.
For minor variations the text of Irenaeus cannot be used satisfactorily, because it is always doubtful whether the Latin version has correctly reproduced the original.

And even in those comparatively small portions where the Greek is still preserved, it has come down to us through the medium of other writers, and we have just had an instance how easily the distinctive features of the text might be obliterated.
Neither of these elements of uncertainty exists in the case of Tertullian; and therefore, as the text of his New Testament quotations has been edited in a very exact and careful form, I shall illustrate what has been said respecting the corruptions introduced in the second century chiefly from him.