The Holy Bible teaches that the God Family currently consists of two fully divine Beings, God the Father and God the Son. However, most nominal Christians believe we should add a third distinct Being, the Holy Spirit, to what is called the “Godhead,” forming a “Trinity,” a term that does not appear anywhere in Scripture. By “rightly dividing the truth” (II Timothy 2:15), one can relatively easily dismiss virtually all the verses used to support this false belief. However, one passage, I John 5:7-8, in four popular translations—the King James, the New King James, the New Living Bible, and the Amplified Bible Classic—appears to support the Trinity doctrine by using additional verbiage missing from most other translations.
In the New King James Version, the following italicized words were added, apart from the majority of ancient manuscripts: “For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one. And there are three that bear witness on earth: the Spirit, the water, and the blood; and these three agree as one."
According to Anthony and Richard Hanson, professors of theology, in their book, Reasonable Belief, the troubling language
was added by some enterprising person or persons in the ancient Church who felt that the New Testament was sadly deficient in direct witness to the kind of doctrine of the Trinity which he favoured and who determined to remedy that defect. (1980, p. 171).
From The Big Book of Bible Difficulties, by Norman L. Geisler and Thomas Howe, we read:
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 NT 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 I John. (2008, pp. 540-541)
The wise Christian remains alert to the constant threat of our cunning and beguiling adversary, Satan the Devil, to contaminate God's truth (II Corinthians 11:3; 2:11; Genesis 3:1; Ephesians 6:11-12). The false doctrine of the Trinity is foundational to many of the aberrant Protestant and Catholic beliefs. It is not by coincidence, then, that deceptive verbiage was added to a passage devoted, not only to proving the authenticity of Jesus Christ as the Messiah, but also to identifying key characteristics of His true disciples. In doing so, the Trinity doctrine is used to deceive professing Christians by introducing a false third Being into the God Family, as well as to overshadow a major precept of our faith.