'Testimony is True' in the Bible

Jesus answered and said to them, Though I testify concerning myself, yet my testimony is true: for I know whence I came, and whither I go; but ye cannot tell whence I come, and whither I go.

And he that saw it, testified, and his testimony is true: and he knoweth that he speaketh truth, that ye may believe.

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

This testimony is true: wherefore rebuke them sharply, that they may be sound in the faith;

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