The one who overcomes the world believes that Jesus is the Son of God (5:6). John uses the full title of Jesus as the “Son of God.” He has described Jesus and the Father throughout the letter. In 1:3 our fellowship is with God the Father and with “Jesus Christ his son.” In the previous paragraph John stated the Father has sent the Son to be the savior of the world and that God will abide only those who acknowledge Jesus as the Son of God (4:13-16).
But there is a bit of controversy over the text of 1 John 5:7. Compare the KJV with any modern translation” The KJV reads “testify in heaven: the Father, the Word and the Holy Spirit, and these three are one.” These words do not appear in most modern translations although they are usually in a footnote. The verse seems like solid proof text for the doctrine of the Trinity. So why do the words not appear in any modern translation?
Some later manuscripts of the Latin Vulgate had “testify in heaven: the Father, the Word and the Holy Spirit, and these three are one. 8 And there are three that testify on earth:” These words were not in any Greek manuscript before the fourteenth century and did not appear in Latin Bibles until after AD 800. Likely this was a marginal comment which was introduced to the text by a scribe who thought it ought to be inserted. He was either mistaken, or thought it was a god place for a solid Trinity reference and he added it in.
The handful of Greek manuscripts which did have the words were influenced by the reading in the Latin Bible. Erasmus omitted the line from his first two editions of his Greek New Testament, and was criticized by Catholic scholars who used the Vulgate as a proof text for the doctrine of the Trinity.
Erasmus told his critics that if even one Greek manuscript could be found with the line, he would add it to the next edition. A manuscript was quickly prepared (codex 61, the work of a Franciscan monk named Froy or Roy), and Erasmus added the line to the next addition of his GNT, although with a note explaining that he doubted the line was genuine. The four manuscripts that support the longer reading are ms. 61 (sixteenth century), ms. 88 (twelfth century), ms. 629 (fourteenth or fifteenth century), and ms. 635 (eleventh-century manuscript with the passage written in its margin during the seventeenth century).
Metzger reports that codex 61, which is housed at the library of Trinity College in Dublin, “almost opens of its own accord to 1 John 5–so often has it been consulted on this passage!” (The Text of the New Testament, 101, note 5). However, Peter Malik says the manuscript has an abundance of marginal notes added by two different hands after the codex was produced (in Hixson and Gurry, Myths and Mistakes, 158).
What does it matter? This is not a case of removing the Trinity from the Bible as some more conspiracy-minded people might suggest. This is a good example of textual critics doing their job and determining the most accurate form of the text from the existing variants. The doctrine of the Trinity does not stand (or fall) on 1 John 5:7. In fact, 1 John 5:6 mentions the Son and the Spirit together with God in verse 8. There are plenty of examples of Father-Son equality in the Gospel of John.
Does the lack of the words “the Father, the Word and the Holy Spirit, and these three are one” change any Christian’s faith in the Trinity? If it does, then that faith was thin to begin with.