For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one (I John 5:7).
This is the most explicit statement in the Bible of the doctrine of the Trinity, but also the most controversial. It is found in most old Latin manuscripts of the Bible, but only in a few of the Greek manuscripts. Most modern English translations omit it altogether, but the doctrine of the Trinity does not depend only on this verse (see Matthew 28:19; II Corinthians 13:14; Ephesians 2:18; John 14:16,17, etc.).
It is called the Johannine Comma, because of its parenthetical position tying together verses 6 and 8. The question is whether it was originally an insertion from a marginal note by some pious Trinitarian scribe or an arbitrary excision by some anti-Trinitarian copyist during the Arian controversies of the fourth century. Entire books have been written about this verse on both sides of the controversy.
Many gnostic pseudo-Christians opposed the idea of the divine Trinity in those early centuries, as did the Jews and, of course, the Muslims and their Koran (Mohammeds book is vehemently antagonistic toward the Trinity doctrine, consigning all who believe it to perdition). There would be a real incentive to early doubters to try to get rid of such a clear-cut statement of the Trinitymore so, it would seem, then any incentive by a genuine Christian to tamper with Gods inspired word by adding to it (note the dire warning against such presumption in Revelation 22:18). And the verse does make beautiful sense in its context.
The King James translators fully understood the evidence on both sides and were all highly capable scholars. They opted to keep the verse. In any case, with it or without, our God of creation and redemption is indeed one triune GodFather, Son, and Holy Spirit. HMM