Nearly all modern commentators (Barnes, Robertson, Ellicott, Expositor's) highlight that the famous Trinitarian phrase in this verse ("the Father, the Word, and the Holy Ghost: and these three are one") is absent from the earliest and most reliable Greek manuscripts. It is widely considered a later addition, likely a scribe's marginal note that was eventually copied into the main text. The original letter almost certainly focused only on the Spirit, water, and blood as witnesses.