Priscillian of Avila (AD 340-85) provides the earliest (undisputed) attestation to the Latin insertion into the text of 1 John, known as the Johannine Comma. Priscillian's death in 385 was by way of capital punishment for allegedly practicing sorcery. Priscillian is, therefore, sometimes viewed as being the first professing Christian put to death (through the use of the power of the state) by professing Christians on what appear to be religious grounds.
Priscillian's works were long thought to be lost or existent only as fragments quoted by others, but in 1885, Georg Schepss (re-)discovered several tractates by him and/or a close follower. These tractates are significant to our evaluation of the teachings of Priscillian and the Priscillianism that followed him, but also significant to the history of the textual transmission of the Latin insertion of the heavenly witnesses found in many later Latin manuscripts of 1 John.
Interestingly, the version of the Johannine Comma that Priscillian attributes to John is one in which the earthly witnesses are presented first and three are said to be one "in Christ Jesus." In other (later-attested) versions of the Johannine Comma, the heavenly witnesses are presented first and "in Christ Jesus" is not present. Additionally, the expression translated as "testify" is presented as "testimonium dicunt" (lit. declare testimony). Finally, there is an interesting difference as to what the earthly witnesses are in Priscillian.
Interesting for my friend Nick Sayers, Priscillian describes Christ as him "qui fuit, est et futurus est" (lit. which has been, is, and will be), which one would expect Nick to see as a reference (or possible reference) to KJV Revelation 16:5, although neither the CSEL nor Marco Conti make that connection.
The controversy over Priscillianism came to the attention of Jerome. In his "Of Illustrious Men," Jerome's 121st entry (written around AD 393, less than a decade after Priscillian's death) reads:
Priscillianus, bishop of Abila, belonged to the party of Hydatius and Ithacius, and was put to death at Trèves by the tyrant Maximus. He published many short writings, some of which have reached us. He is still accused by some, of being tainted with Gnosticism, that is, with the heresy of Basilides or Mark, of whom Irenaeus writes, while his defenders maintain that he was not at all of this way of thinking.
However, Jerome's Letter 133, to Ctesiphon, approximately AD 415 (thirty years after Priscillian's death), states (section 3):
Then there is Priscillian in Spain whose infamy makes him as bad as Manichaeus, and whose disciples profess a high esteem for you. These are rash enough to claim for themselves the twofold credit of perfection and wisdom. Yet they shut themselves up alone with women and justify their sinful embraces by quoting the lines:
The almighty father takes the earth to wife;
Pouring upon her fertilizing rain,
That from her womb new harvest he may reap.
These heretics have affinities with Gnosticism which may be traced to the impious teaching of Basilides. It is from him that you derive the assertion that without knowledge of the law it is impossible to avoid sin. But why do I speak of Priscillian who has been condemned by the whole world and put to death by the secular sword?
Similarly, in section 4:
Leaving ancient history I will pass to times nearer to our own. Arius intent on leading the world astray began by misleading the Emperor's sister. The resources of Lucilla helped Donatus to defile with his polluting baptism many unhappy persons throughout Africa. In Spain the blind woman Agape led the blind man Elpidius into the ditch. He was followed by Priscillian, an enthusiastic votary of Zoroaster and a magian before he became a bishop. A woman named Galla seconded his efforts and left a wandering sister to perpetuate a second heresy of a kindred form. Now also the mystery of iniquity is working. 2 Thessalonians 2:7 Men and women in turn lay snares for each other till we cannot but recall the prophet's words: the partridge has cried aloud, she has gathered young which she has not brought forth, she gets riches and not by right; in the midst of her days she shall leave them, and at her end she shall be a fool.
Thus, we see that Jerome's information about Priscillian seems to have evolved and that his opinion did not improve over time.
Oxford University Press published a translation by Marco Conti of Priscillian's Tractate 1 (among other writings). Lines 46-48 of the Tractate are relevant portion, found in the Latin original (taken from CSEL 18) at p. 34 and in the English translation at p. 35. The Latin text is taken from a manuscript that the CSEL places in the 5th or 6th century.
Latin (ll. 28-48) (corresponding to the Latin at pp. 5-6 of CSEL 18, specifically p. 5, l. 6, to page 6, l. 9):
Quis enim est qui legens scribturas et unam fidem unum baptisma unum deum [Eph 4:5-6.] credens hereticorum dogmata stulta non darnnet, qui, dum uolunt humanis conparare diuina, diuidunt unitam in dei uirtute substantiam et magnitudinem Christi tripertito ecclesiae fonte uenerabilem Binionitarum scelere partiuntur, cum scribtum sit: ego sum deus et non est alius praeter me iustus [Is 45:21.] et saluator non es praeter me, [Hos 13:14.] et: ego primus et ego posthaec et praeter me non est deus, [Is 44:6.] quis sicut ego? [Is 44:7.] item alibi: ego sum et ante me non fuit alius, et post me non erit similis mihi; ego deus et non est praeter me qui saluos faciat, [Is 43:10-11.] et iterum Moyse dicente: dominus deus noster deus unus est,[Deut 6:4.] et Hieremias ait: hic est deus noster nec reputabitur alius absque eum qui inuenit omnem uiam sapientiae et dedit eam Jacob puero suo et Istrahel dilecto suo; posthaec in terris uisus est et cum hominibus conuersatus est.[Baruch 3:36-8.] Ipse est enim qui fuit, est et futurus est et uisus a saeculis uerbum caro factus inhabitauit in nobis [Jn 1:14.] et crucifixus deuicta morte uitae heres effectus est ac tertia die resurgens factus futuri forma spem nostrac resurrectionis ostendit et ascendens in caelos uenientibus ad se iter construit totus in patre et pater in ipso, [Cf. Jn 14:11.] ut manifestaretur quod scribtum est: gloria in exeelsis deo et pax hominibus in terra bonae uoluntatis;[Lk 2:14.] sicut Iohannes ait: tria sunt quae testimonium dicunt in terra: aqua, caro et sanguis et haec tria in unum sunt, et tria sunt quae testimonium dicunt in caelo: pater, uerbum et spiritus et haec tria unum sunt in Christo Jesu.[1 John 5:8,7.]
English:
For who is that who, reading the Scriptures and believing 'in one faith, one baptism, one God', [Eph 4:5-6.] does not condemn the foolish doctrines of the heretics who, while they want to put divine things in the same class with the human, divide the substance united in the power of God and break up the venerable greatness of Christ in the tripartite fountain of the church with the crime of the Binionites, because it was written: 'I am God and there is no other who is just but me', [Is 45:21.] and 'there is no saviour besides me',[Hos 13:14.] and 'I am the first and I am after this and besides me there is no god';[Is 44:6.] [and] 'who is like me?';[Is 44:7.] and likewise in another passage: 'I am and before me there shall be no similar to me; I am God and besides me there is nobody who may save';[Is 43:10-11.] and Moses says again: 'The Lord is our God, the only God,'[Deut 6:4.] and Jeremiah declares: 'This is our Lord and no other but him shall be considered, who found all the way of wisdom and gave it to Jacob his servant to Israel his beloved; after this he was seen on earth and lived with men'?[Baruch 3:36-8.] He is that who was, is, and shall be, and appeared as 'the Word' from eternity, 'was made flesh, dwelled in us and',[Jn 1:14.] after being crucified, since death had been conquered, was made heir of life; and by rising on the third day, as he was made the type of future, he showed the hope of our resurrection, and be ascending to the heavens he built the path for those who came to him, while he was 'all in the Father and the Father in him',[Cf. Jn 14:11.] so that what was written might be manifested: 'Glory to God in the highest and peace on earth to people of good will;'[Lk 2:14.] [and] as John says: 'There are three who testify on earth, the water, the flesh, and the blood, and these three are in one, and there are three who testify in heaven, the Father, the Word, and the Spirit, and these three are one in Jesus Christ.'[1 John 5:8,7.]
I have preserved (or at least attempted to accurately transcribe) Conti's English as it is found at p. 35 of the work. I note that the inclusion of the quotation around the "and" for John 1:14 is probably an error in the English (as it does not align with the Latin).
The quotation is of interest as it pertains the prologue of Ps-Jerome. While it possible that a Priscillianist scribe added the comma reference to bolster Priscillian's tractate after Priscillian's death, the existence of a 5th or 6th century manuscript having such a text demonstrates, at least, that this was not a medieval insertion into Priscillian's work. It is an interesting question for scholars of Priscillian to try to determine the extent to which Priscillian's followers may have interpolated his works after his passing. In the specific case of the tractates re-discovered by Schepss, it is believed that four of the eleven tractates were written by a close follower of Priscillian, rather than by Priscillian himself, even though the tractates are attributed to Priscillian.
Assuming that the tractate is genuine (as is generally accepted) and that this portion is original to the tractate (which has not been, to my knowledge, disputed), this would provide a fourth-century date for the first clear emergence of a form of the Johannine Comma.
This emergent form is not, however, the same as the form of the Johannine Comma provided in Theodore Beza's 1598 edition (the most likely source for the KJV text of 1 John 5:7-8)(p. 506):
Beza's Latin based on Beza's Greek:
Nam tres sunt qui testificantur in caelo, Pater, Sermo, & Spiritus sanctus: et hi tres unum sunt. Et tres sunt qui testificantur in terra, Spiritus, et aqua, et sanguis: et hi tres unum sunt.
Latin Vulgate as reported by Beza:
Quoniam tres sent qui testimonium dant in caelo, Pater, Verbum, et Spiritus sanctus: et hi tres unum sunt. Et tres sunt qui testimonium dant in terra, Spiritus, aqua, et sanguis: et hi tres unum sunt.
Compare with Priscillian's Latin:
... tria sunt quae testimonium dicunt in terra: aqua, caro et sanguis et haec tria in unum sunt, et tria sunt quae testimonium dicunt in caelo: pater, uerbum et spiritus et haec tria unum sunt in Christo Jesu.
You can see that there is a slight difference between "delivery testimony" (Priscillian) "give testimony" (Beza's Vulgate) and "testify" (Beza's own). There is also a different word choice by Beza of "Sermo" instead of "Verbum," the former connoting the spoken word. The difference between "tres" and "tria" is the difference between masculine and neuter, but the meaning of each is "three". Similarly, "hi" is masculine, whereas "haec" is neuter, but each mean "these". Likewise, "quae" is neuter and "qui" is masculine, but both mean "which". There is also the difference between "nam" (Beza) and "quoniam" (Vulgate), with the latter being more specifically "because," but the meaning being roughly the same. As noted above, the three earthly witnesses are first for Priscillian, but second for Beza and his Vulgate. Also, Priscillian's version includes "in Christ Jesus," which Beza and his Vulgate omit. Moreover, Priscillian's version has "Spiritus" but lacks "sanctus." Finally, the order of the three earthly witnesses is different and "caro" (flesh) is found rather than "spiritus" (spirit).
Assuming for the sake of argument that Jerome was familiar with Priscillian's Tractate I in the form we know it, such familiarity would make it possible for Jerome to have opined on the difference in translation between that set forth by Priscillian and the more common Old Latin translation that did not mention the three heavenly witnesses. On the hypothesis that Jerome saw the tractate and the spurious addition to John's epistle, this would explain his mention of "unfaithful" translators adding to the words that were written. On the other hand, I see no evidence that Jerome knew of our interacted with this treatise anywhere (and I do not believe the Ps-Jerome prologue to be Jerome's).
Interestingly, though, Basilides (mentioned by Jerome) is believed to have produced a lengthy commentary on the Gospel of John, all of which is now lost. If - as Jerome avers - Priscillian was influenced by Basilides, then it is possible that Priscillian's attribution to John is dependent on his reception of Basilides work. If that were the case, that would push the Johannine Comma back to the second century (Basilides was apparently active from AD 117-161). However, we are now firmly in the realm of speculation.
The work of Priscillian, who lived in what is now Spain, also has potential interest as it relates to the presumably later citation found in Victor of Vita's work (discussed here). Although there is variation in the text of Victor's work among the extant manuscripts thereof, the reconstructed text is this:
tres sunt qui testimonium perhibent in caelo, pater, uerbum et spiritus sanctus, et hi tres unum sunt.
You will notice that the relation to the earthly witnesses is not able to be determined from this quotation. One assumes that "in Christ Jesus" is not present in the text from which Victor's work quotes. Like Beza's Vulgate text, masculine pronouns and masculine "three" are used, and the spirit is called "holy," but "testimonium perhibent" (lit. present testimony) is used. According to the critical notes for Victor's work, at least one copies uses "dant" like Beza's Vulgate, and at least one omits "sanctus" like Priscillian's. Moreover, seemingly the consensus of three manuscripts is "et filius" (and the son) rather than uerbum (word).
Suffice to say that it does not seem that the text in Victor is precisely the text in Priscillian, whether or not the reconstruction has been done correctly. Note as well the difficulty in drawing firm conclusions about the exact wording of the text from the manuscripts of Victor's writings, and consider how this is heightened in the case of Priscillian, for whom we are apparently reliant on a single manuscript.
