John 21:24
This is the disciple who is testifying about these [things], and who has written down these [things]. And we know that his testimony is true.
John 19:35
And the one who has seen [it] has testified, and his testimony is true, and that person knows that he is telling the truth, so that you also may believe.
3 John 1:12
Demetrius has been testified to by all, even by the truth itself. And we also testify [to him], and you know that our testimony is true.
John 15:27
And you also will testify, because you have been with me from the beginning.
1 John 1:1-2
What was from the beginning, what we have heard, what we have seen with our eyes, what we have looked at and our hands have touched, concerning the word of life--
1 John 5:6
This is the one who came by water and blood--Jesus Christ, not with the water only, but with the water and with the blood. And the Spirit is the one who testifies, because the Spirit is the truth.