John 21:24
This is the disciple who gives witness about these things and who put them in writing: and we have knowledge that his witness is true.
John 19:35
And he who saw it has given witness (and his witness is true; he is certain that what he says is true) so that you may have belief.
3 John 1:12
Demetrius has the approval of all men and of what is true: and we give the same witness, and you are certain that our witness is true.
John 15:27
And you, in addition, will give witness because you have been with me from the first.
1 John 1:1-2
That which was from the first, which has come to our ears, and which we have seen with our eyes, looking on it and touching it with our hands, about the Word of life
1 John 5:6
This is he who came by water and by blood, Jesus Christ; not by water only but by water and by blood.