However it does seem to be referred to by Cyprian writing in the first half of the 3rd century.
Treatise on the Unity of the Church, Paragraph 6
ccel.org/ccel/schaff/anf05.iv.v.i.html?scrBook=1John&scrCh=5&scrV=7#iv.v.i-p33.1
Before we look at Cyprian per se, a little background is needed. The Comma occurs only in about 8 manuscripts, mostly in the margins, and all of them quite late. Bruce Metzger, in his
Textual Commentary on the Greek New Testament (2nd edition), after commenting on the manuscript testimony, says this (p. 648):
(2) The passage is quoted in none of the Greek Fathers, who, had they known it, would most certainly have employed it in the Trinitarian controversies (Sabellian and Arian). Its first appearance in Greek is in a Greek version of the (Latin) Acts of the Lateran Council in 1215.
(3) The passage is absent from the manuscripts of all ancient versions (Syriac, Coptic, Armenian, Ethiopic, Arabic, Slavonic), except the Latin; and it is not found (a) in the Old Latin in its early form (Tertullian Cyprian Augustine), or in the Vulgate (b) as issued by Jerome or (c) as revised by Alcuin.
Although Cyprian uses 1 John to argue for the Trinity, he appeals to this as an allusion via the three witnesses—“
written of”—rather than by quoting a proof-text. Cyprian did not say “
written that.” The current standard critical editions of the Greek New Testament (NA27 and UBS4) actually considers Cyprian a witness
against the Comma.
The earliest instance of the passage being quoted as a part of the actual text of the Epistle is in a 4th century Latin treatise entitled
Liber Apologeticus (chap. 4), attributed either to the Spanish heretic Priscillian (died about 385) or to his follower Bishop Instantius. Apparently the gloss arose when the original passage was understood to symbolize the Trinity (through the mention of three witnesses: the Spirit, the water, and the blood), an interpretation that may have been written first as a marginal note that afterwards found its way into the text.
Daniel Wallace goes more into that
here.
Fast forward twelve centuries later. In his haste in producing the
Textus Receptus, Erasmus made a considerable number of translation mistakes in the process. He was unable to find a manuscript containing the entire Greek New Testament, so he compiled several different sources. After comparing what writings he could find, Erasmus wrote corrections between the lines and sent the documents to Froben. Erasmus said the resulting work was “thrown headlong rather than edited”. He fixed many but not all of the resulting mistakes in the second edition, published in 1519. The Comma did not appear until the third edition, published in 1522.
Its absence from the first two editions has traditionally been explained as the result of the animosity this provoked among churchmen and scholars, led by Lopez de Zúñiga, one of the Complutensian editors. Erasmus is said to have replied to these critics that the Comma did not occur in any of the Greek manuscripts he could find, but that he would add it to future editions if it appeared in a single Greek manuscript.
Such a manuscript was subsequently concocted by a Franciscan and Erasmus, true to his word, added the Comma to his 1522 edition, but with a lengthy footnote setting out his suspicion that the manuscript had been prepared expressly to confute him. This third edition became a chief source for the KJV, thereby fixing the Comma firmly in English-language Bibles for centuries.
The story of Erasmus’ promise has been accepted as fact by scholars, repeated by even so eminent an authority as Bruce M. Metzger. Nevertheless, it can be traced back no further than the first decades of the 19th century, and a 1980 paper by Professor H.J. De Jonge concludes that no such promise was ever made by Erasmus, and that he never suspected the fraudulent
Codex Britannicus (MM 61, the text prepared by the Franciscan) of having been written with the express purpose of forcing him to include the Comma.
Rather, Erasmus included the Comma because he wished to avoid any suspicion of personal unorthodoxy which might undermine the acceptance of his translation: “
For the sake of his ideal Erasmus chose to avoid any occasion for slander rather than persisting in philological accuracy and thus condemning himself to impotence. That was the reason why Erasmus included the Comma Johanneum even though he remained convinced that it did not belong to the original text of 1 John.”
In 1546, Trent defined the Biblical canon for the Church, confirming all books traditionally accepted as canonical and therefore inspired. The fathers decided to canonize “
the entire books with all their parts, as these have been wont to be read in the Catholic Church and are contained in the old Latin Vulgate.” Though the revised Vulgate contained the Comma, the earliest known copies of the Vulgate did not. Therefore the Council’s decrees did not necessarily confirm Comma Johanneum as canonical.
On 13 January 1897, the Holy Office decreed that Catholic theologians could not “with safety” deny or call into doubt the Comma’s authenticity. Pope Leo XIII approved this decision two days later, though his approval was not
in forma specifica - that is, Leo XIII did not invest his full papal authority in the matter, leaving the decree with the ordinary authority possessed by the Holy Office. Three decades later, on 2 June 1927, Pope Pius XI decreed that the Comma Johanneum was open to dispute.
