The context of the so-called allusion to the Comma Johanneum in Against Praxeas 25.1.
Tertullian was a Montantist.
Listen to his words.
TERTULLIAN OF CARTHAGE (circa. 145-225.C.E. ): “In divers ways has the Devil shown hostility to the Truth. At times he has tried to shake it by pretending to defend it. He is the champion of the one Lord, the Almighty, the creator of the world,
so that he may make a heresy out of the unity. He says that the Father himself came down into the virgin, himself was born of her, himself suffered, in short himself is Jesus Christ. The serpent has forgotten himself: for when he tempted Jesus Christ after the baptism of John it was as Son of God that he attacked him, being assured that God has a son at least from those very scriptures out of which he was then constructing the temptation : "If thou art the Son of God, command that these stones be made bread" [1]: again, "If thou art the Son of God cast thyself down from hence, for it is written that he - the Father, of course – hath given his angels charge concerning thee, that in their hands they should bear thee up, lest in any place thou dash thy foot against a stone." [2] Or will he accuse the gospels of lying, and say, "Let Matthew and Luke see to it: I for my part approached God himself, I tempted the Almighty hand to hand: that was the reason for my approach, that was the reason for the temptation: otherwise, if it had been <only> God's son, perhaps I should not have demeaned myself < to tempt> him"? Nay but he himself rather is a liar from, the beginning,[3] and so is any man whom he has suborned with his own <coin>,
like Praxeas. For this person was the first to import to Rome out of Asia this kind of wrong headedness a man generally of restless character, and moreover puffed up with boasting of his confessorship on account of nothing more than a mere short discomfort of imprisonment: though even if he had given his body to be burned he would have profited nothing, since he had not the love of God[4]
whose spiritual gifts he also drove out by assault. For at that time the bishop of Rome was on the point of recognising
the prophecies of Montanus and Prisca and Maximilla, and as a result of that recognition was offering peace to the churches of Asia and Phrygia; but this man, by false assertions concerning
the prophets themselves and their churches, and by insistence on the decisions of the bishop's predecessors, forced him both to recall the letters of peace already issued and to desist from his project of receiving
the spiritual gifts. Thus Praxeas at Rome managed two pieces of the devil's business: he
drove out prophecy and introduced heresy: he
[Latin "fugavit" ] put to flight the Paraclete and crucified the Father. Praxean tares [1] were sown above the wheat and had germinated here also, while many were asleep in simplicity of doctrine. Thereafter they were brought to light, by whom God would, and seemed even to have been rooted up. In fact the teacher gave security for amendment by return to his former opinions, and his bond remains
in the custody of the natural men,[2] in whose presence the transaction was then carried out. After that, silence. I for my part was subsequently [Latin "disiunxit"] separated from the natural men by my acknowledgement and defence of the Paraclete. But those tares had at that time scattered their seed everywhere, and so for a time it lay hid, deceptively dissembling its life, and has now burst forth anew. But it shall also be plucked up anew, if the Lord will, in the time now at my disposal: if not, then in its due time all counterfeit grain will be gathered and, along with other offences, be burned up in unquenchable fire...”
- (Chapter 1, Pages 130/131, "TERTULLIAN'S TREATISE AGAINST PRAXEAS," Translated by Canon Ernest Evans, and published by SPCK, 1948.)
[FOOTNOTE 1]: Matt. 4. 3.
[FOOTNOTE 2]: Matt. 4. 6; Ps. 91. 11,12.
[FOOTNOTE 3]: Cf. John 8. 44.
[FOOTNOTE 4]: 1 Cor. 13, 3.
[FOOTNOTE 1]: Matt. 13. 24. ff.
[FOOTNOTE 2]: 1 Cor. 2. 14.
That's the context of so-called the Comma "allusion".
Tertullian had definitely become a Montantist (his words):
"I, for my part, was subsequently separated from the natural men [the Church, i.e. Christianity] by
my acknowledgement and defense of the Paraclete [i.e. Montanus]"
No amount of modern sanitization can change the plain and simple sense of his own words above.
As Jerome, said in Paragraph 19, “Against Helvidius”
Hippolytus also points out, that some Montanists were Sabellian's (Refutation 8.19; 10.26)
"But there are others who
are themselves in nature more heretical. These are Phrygians by birth, and have been deceived through having been overcome by womenkind, called
a certain Priscilla and Maximilla, whom they hold for prophetesses, saying that the Comforter Spirit dwelt in them; and they likewise glorify one Montanus before them as a prophet. So having endless books of these people they go astray, neither judging their statements by reason, nor heeding those that are able to judge, but behave without judgement in the faith they give them,
saying that through them they have learned something more than from the Law and the Prophets and the Gospels. But they glorify these womenkind above Apostles and every gift, so that some of them presume to say that there was something more in them than in Christ. These confess God the Father of the universe and creator of all things like the Church, and all that the Gospel witnesses concerning Christ, but
invent new fasts and feasts and meals of dry food and meals of radishes, saying that they were taught them by the womenkind.
And some of them agree with the heresy of the Noëtians [originator of the Sabellian's] in saying that the Father is the same with the Son,
and that this One became subject to birth and suffering and death.
What Hippolytus says corroborates what Pacain said about Praxaes in Chapter 2, Sections 2(B), Epistle I, [“To Sympronian”] “On the Catholic Name”:
“...Blastus the Greek [mentioned by Irenaeus] is one of them ; Theodotus also, and Praxaes were once teachers of your group, they themselves, also Phrygians [i.e. Montantists] of some notoriety”
Eusebius of Caesarea, “Ecclesiastical History” Book 5. Chapter 14:
“...The enemy of God’s Church, who is emphatically a hater of good and a lover of evil, and leaves untried no manner of craft against men, was again active in causing strange heresies to spring up against the Church. For some persons, like venomous reptiles, crawled over Asia and Phrygia, BOASTING THAT MONTANUS WAS THE PARACLETE, and that the women that followed him,
Priscilla and Maximilla, were prophetesses of Montanus...”
That's just a small part of
the context to Tertullian's heretical "Paraclete" reference along with "qui" (
note, not "et") "tres unum sunt" at Adv. Prax. 25.1.