'Testimony is True' in the Bible

Jesus answered and said to them, Even if I testify of myself, my testimony is true, for I know whence I came and whither I go; but you know not whence I come or whither I go.

He who saw has testified, and his testimony is true, for he knows that he says what is true, that you also may believe.

This is the disciple who testifies of these things and has written them; and we know that his testimony is true.

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

Testimony is borne to Demetrius by all, and by the truth itself; and we also testify, and you know that our testimony is true.