John 21:24

This is the disciple who is testifing of these things, and hath written these things: and we know that his testimony is true.

John 19:35

And he that saw it bore witness, and we know that his testimony is true: and he himself is conscious that he speaketh what is true, that ye might believe.

3 John 1:12

Demetrius hath a good testimony from all men, and from the truth itself: and we also bear our testimony, and ye know that our testimony is true.

John 15:27

and ye too shall bear your testimony, because ye have been with me from the beginning.

1 John 1:1-2

THAT which was from the beginning, which we have seen with our eyes, which we have gazed upon, and our hands have handled of the word of life;

1 John 5:6

This is he who came by water and blood, Jesus the Messiah; not by the water only, but by the water and the blood: and the Spirit is the witnessing person, because the Spirit is the truth.

Treasury of Scripture Knowledge

Summary

This is the disciple which testifieth of these things, and wrote these things: and we know that his testimony is true.

Bible References

We know

John 19:35
And he that saw it bore witness, and we know that his testimony is true: and he himself is conscious that he speaketh what is true, that ye might believe.
1 John 1:1
THAT which was from the beginning, which we have seen with our eyes, which we have gazed upon, and our hands have handled of the word of life;
1 John 5:6
This is he who came by water and blood, Jesus the Messiah; not by the water only, but by the water and the blood: and the Spirit is the witnessing person, because the Spirit is the truth.
3 John 1:12
Demetrius hath a good testimony from all men, and from the truth itself: and we also bear our testimony, and ye know that our testimony is true.