One of the big names in the history of the Greek New Testament’s transmission is Desiderius Erasmus (d. 1536). Our readers might know him as the man whom Luther debated in his excellent Bondage of the Will. Something not quite as well-known is the fact that the NT in the KJV stands largely on Erasmus’ edition of the Greek NT. The story goes like this (which is a summary of Bruce Metzger’s discussion on pages 100-103 of The Text of the New Testament, 3rd ed.).
For the benefit of the church, Erasmus essentially wanted to publish a Greek New Testament along with his own Latin translation of it. This, however, was more difficult that he thought it would be since he had a hard time finding proper manuscripts of the Greek NT.
Because Erasmus couldn’t find a single Greek NT manuscript, he used several. The primary manuscripts he used were from (roughly) the twelfth century. In fact, since he couldn’t find manuscripts for some parts of Revelation, he translated the old Latin Vulgate back into Greek. These Latin-to-Greek translations, of course, have not been found in any old Greek manuscript; however, they still appear in many (all?) editions of the KJV and NKJV (i.e. certain words Rev 17:4, 22:16—21. See also Acts 9:6).
When his work was finished – or nearly finished – someone pointed out to Erasmus that his Greek text didn’t contain the Trinitarian statement in 1 John (5:7-8 – ‘The Father, the Word, and the Holy Ghost: and these three are one. And there are three that bear witness in earth.’). Here’s how Bruce Metzger discusses this fact.
“Erasmus replied that he had not found any Greek manuscript containing these words, though he had in the meanwhile examined several others besides those on which he relied when first preparing his text. In an unguarded moment Erasmus promised that he would insert the ‘Comma Johanneum’,’ as it is called, in future editions if a single Greek manuscript could be found that contained the passage.”
“At length such a copy was found – or was made to order! As it now appears, the Greek manuscript had probably been written in Oxford about 1520 by a Fransiscan friar named Froy (or Roy), who took the disputed words from the Latin Vulgate. Erasmus stood by his promise and inserted the passage in his third edition (1522), but he indicates in a lengthy footnote his suspicions that the manuscript had been prepared expressly in order to confute him” (p. 101).
“…Thus the text of Erasmus’ Greek New Testament rests upon a half-dozen miniscule manuscripts. The oldest and best of these manuscripts (codex I, a miniscule of the tenth century, which agrees often with the earlier uncial text) he used least, because he was afraid of its supposedly erratic text! …Subsequent editors, though making an umber of alterations in Erasmus’ text, essentially reproduced this debased form of the Greek Testament. Having secured an undeserved pre-eminence, what came to be called the Textus Receptus of the New Testament resisted for 400 years all scholarly efforts to displace it in favour of an earlier and more accurate text” (p. 103).
To read the rest of this fascinating story of the Greek NT’s transmission, you’ll have to get Metzger’s book. Be aware that it is not light and easy reading; it is a seminary level resource (and even dry in some places). However, if you want to be knowledgeable in this area, The Text of the New Testament is one book you’ll have to get. It is worth the effort. (Note: I saw there is a fourth revised edition of Metzger’s book. I’m not referring to that one here – I’m referring to the third edition.)