Expositor's Bible Commentary Commentary 1 John 5:7

"And it is the Spirit that beareth witness, because the Spirit is the truth." — 1 John 5:7 (ASV)

“For there are three that testify: the Spirit, the water and the blood.” Does the author mean that the Spirit still witnesses through the biblical Word in which Jesus’ baptism and death are recounted, or that the Spirit gives witness to the community of the efficacy of the historic baptism and death through the rites of water baptism and communion? Probably the author is pointing to the former as having priority but not so as to exclude the latter. The biblical word confirms the prophetic word that the Spirit prophesied (cf. 2 Peter 1:20–21).

But how does the Spirit give witness in the living voice of prophecy?

Presumably he does it inwardly and supernaturally. The Spirit opens eyes and ears to perceive what God is declaring through his proclaimed word (cf. 1 Corinthians 12:3). He does not declare his own words, but through inward conviction he confirms the proclamation as being indeed the truth (cf. Acts 5:32). The Spirit provides what humanity is unable to acquire for itself. This witness of the Spirit accompanies every presentation of the word.The text contained in the NIV footnote made its way into the KJV through the Latin Vulgate. Most scholars agree that it is a later, though orthodox, addition to the text and is not part of John’s reiginal letter.