There is a popular notion that 1 John 5:7 was interpolated into the Bible sometime in the last 500 to 600 years. The idea comes from the textual critics’ notion that the received text of the Bible must contain errors and that it is the job of modern critics to redact scripture to maintain integrity with the earliest known manuscripts.

Since 1 John 5:7 is not found in any of the ancient Greek manuscripts prior to 1300-1400 AD, then this text must be spurious. This is an accepted idea even among conservatives. Many modern Bible translations include the verse in brackets or as a footnote indicating its late inclusion.

Or so say the critics.

1 John 5:7,8 is the only scripture that contains the Trinitarian formula:

For there are three that bear record [in heaven, the Father, the Word, and the Holy Ghost: and these three are one. And there are three that bear witness in earth,] the spirit, and the water, and the blood: and these three agree in one.

The bracketed text is the Trinitarian doctrine that God is three in one. The doctrine of the Trinity does not fall apart on the basis of the rejection of this one verse. However, it is the only verse that succinctly denies the Oneness, or Jesus-only dotrine, otherwise known as the ancient heresy of modalistic monarchianism.

The problem I have with the modern criticism of 1 John 5:7,8 is that the Latin text is seen as having inferior credibility compared to some ancient Greek manuscripts. One such commentary explains:

This is the only passage in the whole Bible that gives any color to the trinity or “oneness” doctrines. However, the bracketed portion (see above) of this passage is almost universally recognized as an interpolation. It first crept into the Greek text in the fourteenth century. It is true that some late Latin, Vulgate MSS., copied not more than five centuries before, do contain it. This interpolation was first inserted into some Vulgate manuscript and was in the fourteenth century translated into the first Greek text having it. Had this text been in the Bible when the trinitarian controversies were going on, in the fourth to the eighth centuries, certainly the trinitarians who were hard pressed by their opponents to produce such a text, would have used it as a proof text. But none of them ever appealed to John as the author of this, for the good reason that it was then not in the Bible. It doubtless crept into the Latin text by a copyist taking it from the margin, where it was written by somebody as his comment on the text, and inserting it into the Latin text itself, from which, as just said, it was first translated into a Greek manuscript in the fourteenth century. The next Greek manuscript that contains it is from the fifteenth century.

http://godandson.reslight.net/1john-5-7.html

The problem for the textual critics concerning the so-called “Johannine Comma” is that there exist writings of Greek and Latin church fathers who seem to quote this text. Whether the text was in Latin or Greek doesn’t detract from the validity of its reliability. From the third century on, the theology of the western church was written mainly in Latin. Since we have no complete manuscript of the New Testament in Greek from this time, there is no way of knowing whether the Greek text of 1 John 5 contained the phrase “the Father, the Word, and the Holy Ghost: and these three are one.”

There is the idea that God was obligated to transmit a Greek manuscript for every authentic verse of scripture. However, there is no reason to assume that the Latin received text is not reliable.

On one hand, we have some second century Greek fathers, such as Irenaeus, Athenagorus and Hippolytus, who were aware of the “three persons in one God” formula. This word, “prosopon,” is the word the earliest writers employed to say, in Greek, ‘One God in three persons.’ The Latin term ‘persona’ is the correlative term to ‘prosopon.’

John Calvin wrote:

Nor, indeed, was the use of the term Person confined to the Latin Church. For the Greek Church in like manner, perhaps, for the purpose of testifying their consent, have taught that there are three ‘prosopa’ in God. All these, however, whether Greeks or Latins, though differing as to the word, are perfectly agreed in substance (John Calvin, Institutes of the Christian Religion, Book I, Chapter XIII, 2).

Calvin was most likely referring to Hippolytus who uses “prosopon” to describe the three persons of the Trinity throughout his refutation of the heresy of modalistic monarchianism.

Hippolytus c. 200 AD. “If, again, he allege His own word when He said, ‘I and the Father are one,’ [John 10:30], let him attend to the fact, and understand that He did not say, ‘I and the Father am one, but are one.’ For the word are is not said of one person, but it refers to two persons, and one power.” (Hippolytus, ‘Against the Heresy of One Noetus’).

In addition, we have direct quotations of “these three are one” verse, referring to the Trinity in John 5:7,8, from the following Latin fathers.

Tertullian c. 200 AD. “These Three are one essence not one Person, as it is said, ‘I and my Father are One’ [John 10:30] in respect of unity of Being not singularity of number” (Against Praxeas, 25).

Cyprian c. 250 AD. “The Lord says, ‘I and the Father are one;’ and again it is written of the Father, and of the Son, and of the Holy Spirit, ‘And these three are one’” (Treatise 8, ch.3).

Priscillian c. 380 AD. “As John says ‘and there are three which give testimony on earth, the water, the flesh the blood, and these three are in one, and there are three which give testimony in heaven, the Father, the Word, and the Spirit, and these three are one in Christ Jesus.’”(Liber Apologeticus)

Eugenius, spokesman for the African bishops at the Council of Carthage, 484 AD. “… and in order that we may teach until now, more clearly than light, that the Holy Spirit is now one divinity with the Father and the Son. It is proved by the evangelist John, for he says, ‘there are three which bear testimony in heaven, the Father, the Word, and the Holy Spirit, and these three are one.”

Several orthodox African writers quoted the verse when defending the doctrine of the Trinity — Vigilius Tapensis, Victor Vitensis, and Fulgentius of Ruspe.

Fulgentius of Ruspe 513 AD. “See, in short you have it that the Father is one, the Son another, and the Holy Spirit another; in person, each is other, but in nature they are not other. In this regard he [Christ] says, `The Father and I, we are one’ [John 10:30]. He teaches us that `one’ refers to their nature and `we are’ to their persons. In like manner it is said, `There are three who bear witness in heaven, the Father, the Word, and the Spirit, and these three are one’ [1 John 5:7]. Let Sabellius hear ‘we are,’ let him hear ‘three,’ and let him believe that there are three Persons” (The Trinity 4:1).

The Latin Textus Receptus. “… the Father, the Word, and the Spirit, and these three are one.” The verse was known to the Greek and Latin fathers. If it was interpolated, it happened far earlier than 1500 AD — the date claimed by some textual critics. In fact, quotations first begin to appear sometime after 200 AD. There is no reason to think of the Trinitarian formula in 1 John 5:7 as a mistake in transliteration or as an intentional forgery.