'Testimony is True' in the Bible

He who saw this has testified so that you also may believe. His testimony is true, and he knows he is telling the truth.

This is the disciple who testifies to these things and who wrote them down. We know that his testimony is true.

This testimony is true. So, rebuke them sharply, that they may be sound in the faith

Demetrius has a good testimony from everyone, and from the truth itself. And we also testify for him, and you know that our testimony is true.