There is a question concerning First John 5:7 in the Old King James and New King James Versions, in which the verse reads,
“For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one (1 John 5:7, NKJV).
Verse 7 of the NASV is the last sentence of verse 6 in the NKJV.
Verse 7 in the NIV is, “For there are three that testify…”
It is believed that a scribe who was writing the Latin, added what the King James has for verse 7.
Read what a couple of scholars say, “It is a matter of record that it appears first, not in the original Greek of the New Testament, but in the Latin translation. The earliest manuscript in which it appears in Greek is a copy made in the sixteenth century” (Clinton R. Gill).
“The passage is absent from every known Greek manuscript except four…These four manuscripts are ms. 61, a sixteenth century manuscript…ms. 88, a twelfth century manuscript…ms. 629, a fourteenth or fifteenth century manuscript…and ms. 635, an eleventh century manuscript which has the passage written in the margin by a seventeenth century hand. The passage is quoted by none of the Greek Fathers, who, had they known it, would most certainly have employed it in the Trinitarian controversies…Its first appearance in Greek is in a Greek version of the (Latin) Acts of the Lateran Council in 1215 (Bruce M. Metzger, A Textual Commentary on the Greek New Testament).
All of this evidence against it is powerful, considering that we have hundreds of ancient manuscripts of the Greek New Testament, and thousands when all Greek New Testament manuscripts are considered.