This is the disciple who is giving testimony about these things and has written them down, and we know his testimony is true.
And the person who saw this happen is giving a true testimony about it. He knows it is true [and is giving it] so that you will believe [it, also].
Demetrius has been given [a favorable] commendation by everyone, and [is commended] by the truth itself. We [apostles] also give him [a favorable] commendation, and you know that our testimony [about these things] is true.
And you will give testimony about me [also], because you men have been with me from the beginning [of my ministry]."
We [apostles] proclaim to you [the truth about Jesus], who existed from the beginning [of time]. We have heard [Him] and seen [Him] with our [own] eyes. We looked at Him, and [even] touched Him with our hands. [See John 20:20]. [So, we proclaim that] He is the word of life [i.e., the life-giving Word]!
This Jesus is the one whose coming [to earth was introduced] by water [at His immersion. See Matt. 3:13] and [completed] by blood [at His crucifixion, John 19:17-37]. He did not come by the water only, but by the water and by the blood. And it is the Holy Spirit who gives testimony [at both of these events], because the Holy Spirit is [always] the truth. [See John 16:13].