You guys are much more familiar with this than I but I have been following along a bit and found this in my digital library. You can probably get more from it than I but here it is
Porson having spoken Pontifically upon the matter of the text of the Three Witnesses,
cadit quµstio, locutus est Augur Apollo. It is of more importance that Bishop Kaye in his calm wisdom, remarks as follows;
444 In my opinion, the passage in Tertullian, far from containing an allusion to 1 John 5:7, furnishes most decisive proof that he knew nothing of the verse. After this, and the acquiescence of scholars generally, it would be presumption to say a word on the question of quoting it as Scripture. In Textual Criticism it seems to be an established canon that it has no place in the Greek Testament. I submit, however, that, something remains to be said for it, on the ground of the old African Version used and quoted by Tertullian and Cyprian; and I dare to say, that, while there would be no ground whatever for
inserting it in our English Version, the question of
striking it out is a widely different one. It would be sacrilege, in my humble opinion, for reasons which will appear, in the following remarks, upon our author.
It appears to me very clear that Tertullian is quoting 1 John 5:7. in the passage now under consideration:
Qui tres unum sunt, non unus, quomodo dictum est, Ego et Pater unum sumus,
etc. Let me refer to a work containing a sufficient answer to Porson, on this point of Tertullians quotation, which it is easier to pass
sub-silentio, than to refute. I mean Forsters
New Plea, of which the full title is placed in the margin.
445 The whole work is worth thoughtful study, but, I name it with reference to this important passage of our author, exclusively. In connection with other considerations on which I have no right to enlarge in this place, it satisfies me as to the primitive origin of the text in the Vulgate, and hence of its right to stand in our English Vulgate until it can be shewn that the Septuagint Version, quoted and honoured by our Lord, is free from similar readings, and divergences from the Hebrew mss.
p. 516.
: or, Porsons Letters to Travis eclectically examined, etc. etc. By the Rev. Charles Forster, etc. Cambridge, Deighton, Bell & Co., and London, Bell & Daldy, 1867.
Roberts, Alexander ; Donaldson, James ; Coxe, A. Cleveland:
. Oak Harbor : Logos Research Systems, 1997, S. 631