A recurring theme throughout the apostle John's writings is the authenticity of Jesus Christ's testimony that He:
1. is the Creator God—the Son of God the Father (John 1:1);
2. is the promised Messiah (John 1:41);
3. is tasked with announcing the coming Kingdom of God, to provide expiation for mankind's sins, and to provide a perfect, living example of “the Way,” before being crucified and resurrected (John 1:29; 18:36-37; 14:6; 19:16-37; 20:1-31).
To that end, I John 5:1-5 presents a foundational description of Christ's followers—those who believe in His authenticity—and how they would display their love for both the Father and the Son and their inspired capacity to overcome the world through their faith.
In verses 6-8, John continues building on this foundation by revealing three of the most significant “witnesses”—all in agreement—to the authenticity of the testimony of Jesus Christ: “the Spirit, the water, and the blood.”
The trouble begins in between, with deceptive language added to verses 7 and 8, again, only in a few translations.
Martin G. Collins
Does I John 5:7-8 Support the Trinity Doctrine?