It is true that this verse has
virtually no support among the early Greek manuscripts, though it is found in
Latin manuscripts. Its appearance in late Greek manuscripts is based on the
fact that Erasmus was placed under ecclesiastical pressure to include it in his
Greek New Testament of 1522, having omitted it in his two earlier editions of
1516 and 1519 because he could not find any Greek manuscripts which contained
it.
Its inclusion in the Latin Bible
probably results from a scribe incorporating a marginal comment (gloss) into
the text as he copied the manuscript of 1 John. But including it in the text
violates almost every rule of textual criticism. Even the New King James
Version, which generally retains the longer readings and disputed passages (see
Mark 16:9-20 and John 7:53-8:11), comments in the margin that this is “a
passage found in only four or five very late Greek mss.” (Norman L.
Geiser and Ron Rhodes, When Cultists Ask: A Popular Handbook on Cultic
Misinterpretations [Grand Rapids, Mich.: Baker Books, 1997], 299)