'Truth' in the Bible

From the elder, to Gaius my dear brother, whom I love in truth.

For I rejoiced greatly when the brothers came and testified to your truth, just as you are living according to the truth.

I have no greater joy than this: to hear that my children are living according to the truth.

Therefore we ought to support such people, so that we become coworkers in cooperation with the truth.

Demetrius has been testified to by all, even by the truth itself. We also testify to him, and you know that our testimony is true.